Risk Factors (Genetics & Inherited Conditions)
Risk factors for obesity include advancing age, quitting smoking, working varied shifts, decreased activity, and a sedentary lifestyle. Other risk factors include an imbalance of excess calories versus decreased activity; a high level of fast-food intake; high alcohol consumption; eating foods with a high glycemic index, including carbohydrates, such as instant mashed potatoes, baked white potatoes, and instant rice; eating until full; and eating quickly.
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Etiology and Genetics (Genetics & Inherited Conditions)
Genetic determinants play a large part in the development of obesity, and more than two hundred genes have now been identified that have some association with obese phenotypes. Alternative alleles at most of these genes may marginally increase one’s susceptibility to obesity, but environmental factors will still largely determine an individual’s overall body size.
Although the gene function is not well understood, genetic variations at the PTER gene, located on the long arm of chromosome 1 at position 1q32-q41, are most strongly associated with childhood obesity and adult morbid obesity. These variations may contribute to as much as one-third of all childhood obesity and 20 percent of adult obesity. Another major player appears to be the NPC1 gene (at position 18q11-q12), since its protein product seems to be involved in controlling appetite. One study estimates that allelic variations at this gene account for about 10 percent of childhood obesity and 14 percent of adult obesity. The MAF gene (at position 16q22-q23) encodes a protein that regulates the production of the hormones insulin and glucagon, key regulators of metabolism. Variants at this locus are estimated to account for about 6 percent of early-onset childhood obesity and 16 percent of adult morbid obesity. The PRL gene (at position 6p22.2-p21.3) specifies the hormone prolactin, which not only stimulates lactation in...
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Symptoms (Genetics & Inherited Conditions)
Symptoms of obesity include increased weight, thickness around the midsection, and obvious areas of fat deposits. Complications of untreated obesity include decreased energy, heart disease, high blood pressure, high blood pressure during pregnancy, type 2 diabetes, gallstones, worsening arthritis symptoms, and an increased risk of certain cancers. Additional symptoms include gout, infertility, sleep apnea, poor self-image, depression, urinary incontinence, and the increased risk of death for individuals who have increased waist circumferences and waist-to-hip ratios.
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Screening and Diagnosis (Genetics & Inherited Conditions)
Obesity is diagnosed by visual exam and body measurements using height and weight tables, body mass index, a caliper to measure body folds, waist-to-hip ratio measurements, and water-displacement tests. The doctor may also order blood tests to rule out other medical conditions that may cause excess body weight.
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Treatment and Therapy (Genetics & Inherited Conditions)
Obesity is difficult to treat. Its treatment is affected by cultural factors, personal habits, lifestyle, and genetics. There are many different treatment approaches. Patients should talk to their doctors or ask for a referral to a specialist; the doctor and specialist can help develop the best treatment plan.
Plans for weight loss may include keeping a food diary, in which patients track everything they eat or drink. Patients should ask their doctors about an exercise program, which is another treatment option. Individuals can add bits of physical activity throughout their days, take stairs instead of elevators, and park a little farther away. Patients can also limit the amount of time they spend watching television and using the computer; this is important for children.
A dietitian can help patients with their total calorie intake goal, which is based on their current weights and weight loss goals. Portion size also plays an important role; using special portion control plates may help patients succeed.
The doctor may recommend that patients reduce saturated and trans fats, limit the amount of refined carbohydrates they eat, and keep fat intake under 35 percent of the total calories eaten daily. Behavior therapy may help patients understand when they tend to overeat, why they tend to overeat, and how to combat overeating habits.
Research on the effectiveness of weight-loss programs is limited....
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Prevention and Outcomes (Genetics & Inherited Conditions)
Preventing obesity can be difficult. There are many factors that influence an individual’s weight. General recommendations include talking to a doctor or a dietician about an appropriate number of calories to eat per day and eating a diet with no more than 35 percent of daily calories from fat. Individuals can follow an appropriate exercise program; limit the amount of time they spend doing sedentary activities, including watching television or using the computer; and talk to their doctors or an exercise professional about working activity into their daily lives. Individuals can also ask a dietitian for help planning a diet that will help them maintain a healthy weight or lose weight if necessary. In addition, individuals can learn to eat smaller portions of food; most Americans eat portions that are too large.
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Further Reading (Genetics & Inherited Conditions)
EBSCO Publishing. DynaMed: Obesity. Ipswich, Mass.: Author, 2009. Available through http://www .ebscohost.com/dynamed.
_______. Health Library: Obesity. Ipswich, Mass.: Author, 2009. Available through http://www .ebscohost.com.
Goldman, Lee, and Dennis Ausiello, eds. Cecil Medicine. 23d ed. Philadelphia: Saunders Elsevier, 2008.
Goroll, Allan H., and Albert G. Mulley, Jr., eds. Primary Care Medicine: Office Evaluation and Management of the Adult Patient. 6th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2009.
Maruyama, K., et al. “The Joint Impact on Being Overweight of Self-Reported Behaviours of Eating Quickly and Eating Until Full: Cross-Sectional Survey.”British Medical Journal Clinical Research Edition 337 (2008): a2002. Available through EBSCO DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.
Pedersen, S. D., J. Kang, and G. A. Kline. “Portion Control Plate for Weight Loss in Obese Patients with Type 2 Diabetes Mellitus: A Controlled Clinical Trial.” Archives of Internal Medicine 167, no. 12 (June 25, 2007): 1277-1283.
Pischon, T., et al. “General and Abdominal Adiposity and Risk of Death in Europe.” New England Journal of Medicine 359, no. 2 (November 13, 2008): 2105-2120.
Samuels-Kalow, M. E., et al. “Prepregnancy Body Mass Index,...
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Web Sites of Interest (Genetics & Inherited Conditions)
American Dietetic Association. http://www.eatright.org
Dietitians of Canada. http://www.dietitians.ca
Division of Nutrition Research Coordination of the National Institutes of Health: Dietary Guidelines for Americans. http://dnrc.nih.gov/ncc/2002-NutriBrocCRA2.pdf
Genetics Home Reference. http://ghr.nlm.nih.gov
Health Canada: Canada’s Food Guide. http://www.hc-sc.gc.ca/fn-an/food-guide-aliment/index_e.html
The Obesity Society. http://www.obesity.org
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Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
Obesity is a condition in which the body accumulates an abnormally large amount of adipose tissue, or fat. It is a multifactorial, chronic disease that is rapidly increasing and having devastating effects on health, especially in the United States. The disease has social, cultural, genetic, metabolic, behavioral, and psychological components. People who are obese also face stigma and discrimination in work and social settings. Obesity is the second leading cause of preventable deaths in the United States, resulting in an estimated 300,000 deaths each year.
Because it is not practical to measure body fat content directly but it is easy to measure weight and height, the body mass index (BMI), which correlates closely with body fat, is often used to identify and quantify obesity.
Being overweight and being obese are not the same condition. A BMI of 25 to 29.9 is considered to be overweight, a BMI of 30 or more is obese, and a BMI of 40 or more is severely obese. Approximately 127 million adults in the United States are overweight, 60 million are obese, and 9 million are severely obese. More men than women are overweight (67 versus 62 percent). In 2006, it was estimated that 64.5 percent of adults in the United States were overweight, 30.5 percent were obese, and 4.7 percent were severely obese. This latter figure increased from only 2.9 percent in a 1994 survey done by the National Health and Nutrition Examination...
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Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
Many obese people are highly motivated to lose weight because of the common perception that a slim body build is more attractive than an obese one. Many other overweight individuals desire to lose weight because of health problems related to obesity. As a result, the human and financial resources devoted to weight loss efforts are extensive. Unfortunately, the long-term results of the treatment of obesity are successful in only a minority of cases.
The only measures useful in the treatment of obesity are those that decrease the intake or absorption of calories or those that increase the expenditure of calories. The basis for any long-term weight reduction program is a low-calorie diet. The average daily calorie requirement in the United States is approximately 1,600 calories for women and 2,300 calories for men; decreasing an individual’s intake, usually to between 800 and 1,500 calories, will result in weight loss, provided that energy expenditure does not decrease. A balanced diet, with 20 percent to 30 percent of the calories derived from fat (considerably less fat than is found in the typical American diet) is usually recommended. Many unbalanced diets, or “fad diets,” have enjoyed periods of popularity. Rice diets, low carbohydrate diets, vegetable diets, and other special diets may produce rapid weight loss, but long-term persistence with an unbalanced diet is rare and the lost weight is often regained....
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Fat has several important functions in the human body. It serves as a cushion for the body frame and internal organs, it provides insulation against heat loss, and it is a storage site for energy. Fat stores energy very efficiently since it contains approximately 9 calories per gram, compared with approximately 4 calories per gram in protein and carbohydrate. The presence of reserve stores of energy in the form of fat is particularly important when regular food intake is interrupted and the body becomes dependent on its fat deposits to maintain a source of fuel for daily metabolism and physical activity.
In affluent, culturally advanced societies, however, where food is abundant and modern conveniences greatly reduce the need for physical exertion, many people tend to accumulate excessive amounts of fat, since energy that is taken in but not utilized is stored in the adipose tissue. In the early twenty-first century, health officials were concerned by new findings that showed one in every fifty Americans were “extremely obese,” meaning their BMI measured at least 50 and they were at least 100 pounds overweight. This number had quadrupled since the 1980’s. Obesity is a critical public health problem because it increases the risk of diabetes, hypertension, cardiovascular disease, and other illnesses. Also, many overweight men and women are distressed by the effects of their weight on their social interactions...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
American Academy of Pediatrics. A Parent’s Guide to Childhood Obesity: A Roadmap to Health. Edited by Sandra G. Hassink. Elk Grove Village, Ill.: Author, 2006. A research-based book that gives parents an authoritative yet practical guide to understanding and preventing obesity, including self-assessment inventories, preparing nutritious meals, and coping with challenges.
American Obesity Association. http://www.obesity .org. A comprehensive Web site with information on the disease, research resources, advocacy, disability issues, community action, and personal stories, among many other topics.
Björntorp, Per, ed. International Textbook of Obesity. New York: Wiley, 2001. Text that examines all aspects of obesity, from basic considerations of metabolism, body composition, and etiology, to practical questions of the psychological and medical consequences and the various methods of treatment.
Brownell, Kelly D., and Katherine Battle Horgen. Food Fight: The Inside Story of America’s Obesity Crisis and What We Can Do About It. New York: McGraw-Hill, 2004. A critical examination of the United States’ “toxic environment” of obesity. Explores the roots of the obesity epidemic and its impact on the country’s health and productivity.
Koplan, Jeffrey P., Catharyn T. Liverman, and Vivica I. Kraak, eds. Preventing Childhood Obesity: Health in the Balance....
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Introduction (Psychology and Mental Health)
Unlike the term “overweight,” which is defined as weighing more than a standard level for height and age, “obesity” refers to a person’s having excessive body fat. The body mass index (BMI) is the method most commonly used to assess obesity. BMI measures a person’s weight in relation to his or her height. The World Health Organization (WHO) and the National Heart, Lung, and Blood Institute define obesity as having a BMI of 30 or greater. Obese people are at greater risk for dying and for developing many diseases and conditions, including hypertension (high blood pressure), dyslipidemia (high total cholesterol or high levels of triglycerides), type 2 diabetes, osteoarthritis, sleep apnea or respiratory problems, cardiovascular disease, and certain cancers (endometrial, breast, and colon). Moreover, obese individuals are prone to experiencing numerous psychological and psychosocial effects, such as depression, anxiety, poor body image, and social discrimination. Given these significant and pervasive impacts, identifying factors contributing to obesity and determining effective treatment approaches have become a major public health priority.
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Prevalence (Psychology and Mental Health)
According to the WHO, at least 400 million adults across the world were obese in 2005. According to the Centers for Disease Control, 34 percent of adults in the United States are obese. This is almost a threefold increase in obesity rates in the country since the 1970’s.
Overweight and obesity rates have also been growing rapidly among children in the United States. Since 1980, the number of children who are overweight or obese has tripled from 5 to 17 percent. Multiple studies have shown that approximately 80 percent of children who were overweight at ages ten to fifteen were obese at the age of twenty-five. Further, if children younger than eight are overweight or obese, adulthood obesity is more likely to be chronic and severe.
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Definition and Measurement (Psychology and Mental Health)
Obesity was once considered to be an eating disorder, but the American Psychological Association removed it from the Diagnostic and Statistical Manual of Mental Disorders in the 1980’s, and since then, obesity has largely been considered a medical condition.
Obesity is basically the result of excess fat content in the body. When people have a high energy intake with low energy expenditure, adipose (fatty tissue) cells increase in size, and people gain weight. When people have low energy intake and high energy expenditure, adipose cells shrink in size, and people lose weight. The number of adipose cells (cellularity) is relatively stable within a person. Therefore, people with numerous adipose cells are more likely to become overweight and obese when their energy intake exceeds their energy expenditure.
Skinfold thickness and waist circumference are sometimes used to assess body fat and weight status, but the BMI is most frequently used by researchers and governmental health agencies. BMI measures weight in relation to height and is calculated by dividing weight in kilograms (kg) by height in squared meters (m�). People are considered overweight if their BMI ranges from 25.0 to 29.9 and obese if their BMI is 30.0 or above. The obese category has three subcategories: A BMI between 30.0 and 34.9 is class I obesity, a BMI between 35.0 and 39.9 is class II, and a BMI greater than 40.0 is class III,...
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Who Is Obese? (Psychology and Mental Health)
Obesity rates differ among regional, socioeconomic status, and racial-ethnic groups in the United States. The South has the highest rates of obesity in the United States. In 2007, Mississippi, Alabama, and Tennessee were the only states in which the average BMI was greater than 30.0. These high average BMIs may be due to lower socioeconomic levels and the high-calorie content of traditional southern cooking. Obesity is also higher among people living in rural areas (with populations under 50,000) than those living in urban areas, probably because of limited access to prevention and treatment programs.
Research shows that people of lower socioeconomic status are more likely to be overweight or obese and tend to exercise less than people of higher socioeconomic status. Poverty may lead to a diet high in low-cost, high-calorie packaged foods and fast foods, and may reduce access to treatment or weight-loss programs. Access to fitness centers and safe areas in which to exercise may also be limited.
Rates of obesity and of obesity-related diseases are higher among some racial and ethnic groups. About two-thirds of African American and Latino women are overweight or obese, while slightly less than half of white women are overweight or obese. African Americans have the highest blood pressure rates in the United States, and African Americans and Latinos are about twice as likely to have type 2 diabetes. Native Americans have...
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Possible Causes of Obesity (Psychology and Mental Health)
Because the factors that contribute to obesity—behavior, genes, environment, and familial patterns—are so diverse, the development of obesity can best be explained by the biopsychosocial model. This model assesses obesity in terms of biological factors, psychological factors, and social/environmental factors.Biological Factors
Genetics appear to play a role in obesity. Studies show that family members tend to have similar rates of overweight and obesity, and identical twins, even when raised in different environments, tend to develop similar body sizes. However, having a genetic predisposition to obesity does not mean that people will become obese, but rather that they have a higher risk of obesity in certain psychological, social, or environmental contexts.
A 2006 study conducted by Leslie Olmstead Schulz and colleagues compared obesity rates between two genetically similar Native American tribes, the Pima of southern Arizona and the Nevome of Sonora, Mexico. Obesity is almost nonexistent among the Nevome, who have a diet high in vegetables, grow the majority of their food, and rely largely on manual labor to maintain their agricultural way of life. However, the Pima, who more closely follow mainstream American eating habits and lifestyles, have the highest rates of obesity in the United States. The Pima have a 50 percent higher body weight than the Nevome and develop type 2 diabetes at a rate that is...
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Treatments for Obesity (Psychology and Mental Health)
The treatment of obesity is complicated, long-term, and multimodal in approach. The most common methods of treating obesity, used separately or in combination, are surgical treatment, drug treatment, and behavioral treatment.Surgery
Surgical treatment of obesity is usually considered an option only for those whose BMI is over 40.0 or those who have severe comorbidities that necessitate the immediate and significant loss of weight. Surgical weight-loss treatments are designed to alter the stomach so that it requires much less food to fill it, thus producing satiety after small meals.
Gastroplasty, full and partial gastric banding, and gastric bypass are the typical surgical treatments for obesity. Gastroplasty involves the stapling of the upper stomach, which creates a small pouch that allows only a little food to pass through the stomach at a time. Gastric banding uses bands to separate the stomach into smaller sections. In gastric bypass, the stomach is separated into two pouches, and the small intestine is attached to both sections. Gastric bypass is the most successful of the surgeries at producing weight loss; however, it is also the most risky of the surgeries, resulting in death in approximately 2 percent of patients who undergo it.
Surgical treatments require patients to drastically alter their lifestyle for the remainder of their lives. The kinds and amounts of foods are limited, and food and...
(The entire section is 1128 words.)
Sources for Further Study (Psychology and Mental Health)
Gallagher, D., et al. “How Useful Is Body Mass Index for Comparison of Body Fatness Across Age, Sex, and Ethnic Groups?” American Journal of Epidemiology 143, no. 3 (1996): 228-239. This study of BMI in African Americans and whites looks at the validity of BMI comparisons across race, gender, and ethnic groups.
Hill, J. O. “Can a Small Change Approach Help Address the Obesity Epidemic? A Report of the Joint Task Force of the American Society for Nutrition, Institute of Food Technologies, and International Food Information Council.” American Journal of Clinical Nutrition 89, no. 1 (2009): 1-8. This essay examines whether small changes in daily lifestyle can combat the obesity problem.
Lutes, L. D., et al. “Small Changes in Nutrition and Physical Activity Promote Weight Loss and Maintenance: Three-Month Evidence from the ASPIRE Randomized Trial.” Annals of Behavioral Medicine 35, no. 3 (2008): 351-357. Provides a closer look at the ASPIRE program and how it works.
Schulz, L. O., et al. “Effects of Traditional and Western Environments on Prevalence of Type 2 Diabetes in Pima Indians in Mexico and the U.S.” Diabetes Care 29, no. 8 (2006): 1866-1871. Contrasts the effects of diet in two genetically similar Native American tribes.
Wadden, T. A., and A. J. Stunkard, eds. Handbook of Obesity Treatment. New York: Guilford Press, 2002. A...
(The entire section is 217 words.)
Obesity (Encyclopedia of Medicine)
Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.
Obesity traditionally has been defined as a weight at least 20% above the weight corresponding to the lowest death rate for individuals of a specific height, gender, and age (ideal weight). Twenty to forty percent over ideal weight is considered mildly obese; 4000% over ideal weight is considered moderately obese; and 100% over ideal weight is considered severely, or morbidly, obese. More recent guidelines for obesity use a measurment called BMI (body mass index) which is the individual's weight multiplied by 703 and then divided by twice the height in inches. BMI of 25.99 is considered overweight; BMI over 30 is considered obese. Measurements and comparisons of waist and hip circumference can also provide some information regarding risk factors associated with weight. The higher the ratio, the greater the chance for weight-associated complications. Calipers can be used to measure skin-fold thickness to determine whether tissue is muscle (lean) or adipose tissue (fat).
Much concern has been generated about the increasing incidence of obesity among Americans. Some studies have noted an increase from 12%...
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Obesity (Encyclopedia of Mental Disorders)
Obesity is the condition of having an excessive accumulation of fat in the body, resulting in a body weight more than 20% above the average for height, age, sex, and body type, and in elevated risk of disability, illness, and death.
The human body is composed of bone, muscle, specialized organ tissues, and fat. Together, all of these tissues comprise the total body mass, which is measured in pounds. Fat, or adipose tissue, is a combination of essential fat (an energy source for the normal physiologic function of cells and organs) and storage fat (a reserve supply of energy for future needs). When the amount of energy consumed as food exceeds the amount of energy expended in the normal maintenance of life processes and in physical activity, storage fat accumulates in excessive amounts. Essential fat is tucked in and around internal organs, and is an important building block of all cells in the body. Storage fat accumulates in the chest and abdomen, and, in much greater volume, under the skin.
Causes and symptoms
The human body was designed for life forty thousand years ago, when the ability to store energy in times of plenty meant the...
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Obesity (Encyclopedia of Psychology)
A condition of having an excessive accumulation of fat in the body, resulting in a body weight that is at least 20 percent above normal when measured against standard tables of optimal weight ranges according to age, sex, height, and body type.
Individuals who are 20 percent overweight are considered slightly obese. Those who are 40 percent above standard weight are moderately obese, while those 50 percent above it are morbidly obese. Persons who exceed desired weight levels by 100 pounds (45 kg) or more are hyperobese. Obesity is a serious health problem in the United States. Studies suggests that between 10 and 20 percent of Americans are slightly to moderately obese. Obesity places stress on the body's organs, and is associated with joint problems, high blood pressure, indigestion, dizzy spells, rashes, menstrual disorders, and premature aging. Generally, when compared to persons of normal weight, obese individuals suffer more severely from many diseases, including degenerative diseases of the heart and arteries, and a shorter life expectancy. Obesity can also cause complications during childbirth and surgery.
Obesity may be familial, as the body weight of children appears to be linked to that of their parents. Children of obese parents have been found to be 13 times more likely than other...
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Obesity (Encyclopedia of Children's Health)
Obesity is an abnormal accumulation of body fat, usually 20 percent or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.
The branch of medicine that deals with the study and treatment of obesity is known as bariatrics. As obesity has become a major health problem in the United States, bariatrics has become a separate medical and surgical specialty.
Childhood obesity is in the early 2000s a significant health problem in the United States. Obese children and adolescents are at increased risk for developing diabetes, hypertension, coronary artery disease, sleep apnea, orthopedic problems, and psychosocial disorders.
Obesity involves excessive weight gain and fat accumulation. For children and adolescents, obesity is defined in terms of body mass index (BMI) percentile. BMI is a formula that considers an individual's height and weight to determine body fat and health risk, and it is used differently for children and adolescents than it is for adults. In adults, BMI often misrepresents obesity because it does not consider healthy weight from muscle tissue; therefore, body fat percentage is considered a more...
(The entire section is 2030 words.)
Obesity (Encyclopedia of Alternative Medicine)
Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.
The branch of medicine that deals with the study and treatment of obesity is known as bariatrics. As obesity has become a major health problem in the United States, bariatrics has become a separate medical and surgical specialty.
Obesity traditionally has been defined as body weight at least 20% above the weight corresponding to the lowest death rate for individuals of a specific height, sex, and age (designated as the ideal weight). Twenty to forty percent over ideal weight is considered mildly obese; 4000% over ideal weight is considered moderately obese; and 100% over ideal weight is considered severely, or morbidly, obese. According to some estimates, approximately 25% of the United States population can be considered obese, 4 million of whom are morbidly obese. Other studies state that over 50% of American adults are obese, based on body mass index (BMI) measurements. Excessive weight can result in many serious, and potentially deadly, health problems, including hypertension, Type II diabetes mellitus (non-insulin dependent diabetes), increased risk for coronary disease, increased...
(The entire section is 3330 words.)
Obesity (Encyclopedia of Nursing & Allied Health)
Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.
Obesity is defined by both the U.S. Department of Agriculture and the U.S. Department of Health and Human Services as the presence of a Body Mass Index (BMI) greater than or equal to 30. BMI is a measure of body weight relative to height and is computed as weight/height2, where weight is measured in kilograms and height in meters. Obesity is considered a subset of overweight, which is indicated by a BMI of 25 or higher.
Approximately 55% of the U.S. population is overweight, and almost one in five is obese. Excessive weight can result in many serious, and potentially deadly, health problems, including hypertension, Type II diabetes mellitus (non-insulin dependent diabetes), increased risk for coronary disease, increased unexplained heart attack, hyperlipidemia, infertility, and a higher prevalence of colon, prostate, endometrial, and, possibly, breast cancer. Approximately 300,000 deaths a year are attributed to obesity, prompting leaders in public health, such as former Surgeon General C. Everett Koop, M.D., to label obesity "the second leading cause of preventable deaths in the United States."
Causes and symptoms
The mechanism for excessive weight gain is clearmore calories are consumed than the body burns, and the excess calories are stored as fat (adipose) tissue. However, the exact cause is not as clear and likely arises from a complex combination of factors.
Genetic factors significantly influence how the body regulates the appetite and the rate at which it turns food into energy (metabolic rate). Studies of adoptees confirm this relationshiphe majority of adoptees followed a pattern of weight gain that more closely resembled that of their birth parents than their adoptive parents. Yet genetic factors do not explain the rapid increase in the prevalence of obesity in the U.S. and other industrialized countries in the past 105 years.
A genetic predisposition to weight gain, however, does not automatically mean that a person will be obese. Eating habits and patterns of physical activity also play a significant role in the amount of weight a person gains.
Recent studies have indicated that the amount of fat in a person's diet may have a greater impact on weight than the number of calories it contains. Carbohydrates (cereals, breads, fruits, and vegetables) and protein (fish, lean meat, turkey breast, skim milk) are converted to fuel almost as soon as they are consumed. Most fat calories are immediately stored in fat cells, which add to the body's weight and girth as they expand and multiply.
A sedentary life-style, particularly prevalent in affluent societies, such as in the United States, can contribute to weight gain. Psychological factors, such as depression and low self-esteem may, in some cases, also play a role in weight gain.
At what stage of life a person becomes obese can effect his or her ability to lose weight. Some studies suggest that during two critical periods of a person's lifen early childhood and puberty, excess calories are converted into new fat cells (hyperplastic obesity), while excess calories consumed in adulthood only serve to expand existing fat cells (hypertrophic obesity). Since dieting and exercise can only reduce the size of fat cells, not eliminate them, persons who were obese as children can have great difficulty losing weight, since they may have up to five times as many fat cells as someone who became over-weight as an adult. An estimated 13% of
children ages 61 years and 14% of adolescents ages 129 years are currently overweight.
Obesity can also be a side-effect of certain disorders and conditions, including Cushing's syndrome, a disorder involving the excessive release of the hormone cortisol; hypothyroidism, a condition caused by an underactive thyroid gland; neurologic disturbances, such as damage to the hypothalamus, a structure located deep within the brain that helps regulate appetite; and consumption of certain drugs, such as steroids or antidepressants.
The major symptoms of obesity are excessive weight gain and the presence of large amounts of fatty tissue. Obesity can also give rise to several secondary conditions, including arthritis and other orthopedic problems, such as lower back pain; heartburn; high cholesterol levels; high blood pressure; menstrual irregularities or cessation of menstruation (amenorrhea); shortness of breath that can be incapacitating; and skin disorders, arising from the bacterial breakdown of sweat and cellular material in thick folds of skin or from increased friction between folds.
Diagnosis of obesity is made by observation and by comparing the patient's weight to ideal weight charts. Many doctors and obesity researchers refer to the body mass index (BMI), which uses a height-weight relationship to calculate an individual's ideal weight and personal risk of developing obesity-related health problems.
Since this method can be misleading, due to its failure to account for body composition and muscle mass, physicians may also obtain direct measurements of an individual's body fat content by using calipers to measure skin-fold thickness at the back of the upper arm and other sites. The most accurate means of measuring body fat content involves hydrostatic weighing, or having a person let as much air as possible out of his lungs, immersing him in water and measuring relative displacement; however, this method is very unpleasant and impractical, and is usually only used in scientific studies requiring very specific assessments. Women whose body fat exceeds 32% and men whose body fat exceeds 27% are generally considered obese.
Doctors may also note how a person carries excess weight on his or her body. Studies have shown that this factor may indicate whether or not an individual has a predisposition to develop certain diseases or conditions that may accompany obesity. "Apple-shaped" individuals who store most of their weight around the waist and abdomen are at greater risk for cancer, heart disease, stroke, and diabetes than "pear-shaped" people whose extra pounds settle primarily in their hips and thighs.
Treatment of obesity depends primarily on how overweight a person is and his or her overall health. However, to be successful, any treatment must affect lifelong behavioral changes rather than short-term weight loss. A report issued by the National Institutes of Health-sponsored group, the National Heart, Lung, and Blood Institute, The Practical Guide to Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, recommends a combination of diet modification, increased physical activity, and behavior therapy as the means most likely to prove effective.
"Yo-yo" dieting, in which weight is repeatedly lost and regained, has been shown to increase a person's liklihood of developing fatal health problems more than if the weight had been lost gradually or not lost at all. Behavior-focused treatment should concentrate on:
|HEIGHT AND WEIGHT GOALS|
|Height||Small Frame||Medium Frame||Large Frame|
|5/td>||128-134 lbs.||131-141 lbs.||138-150 lbs.|
|Height||Small Frame||Medium Frame||Large Frame|
|40/td>||102-111 lbs.||109-121 lbs.||118-131 lbs.|
- What and how much a person eats. This aspect may involve keeping a food diary and developing a better understanding of the nutritional value and fat content of foods. It may also involve changing grocery-shopping habits (e.g. buying only what is on a prepared list and only going on a certain day), timing of meals (to prevent feelings of hunger, a person may plan frequent, small meals), and actually slowing down the rate at which a person eats.
- How a person responds to food. This may involve understanding what psychological issues underlie a person's eating habits. For example, one person may binge eat when under stress, while another may always use food as a reward. In recognizing these psychological triggers, an individual can develop alternative coping mechanisms that do not focus on food.
- How they spend their time. Making activity and exercise an integrated part of everyday life is a key to achieving and maintaining weight loss. Starting slowly and building endurance keeps individuals from becoming discouraged. Varying routines and trying new activities also keeps interest high.
For most individuals who are mildly obese, these behavior modifications entail life-style changes they can make independently while being supervised by a family physician. Other mildly obese persons may seek the help of a commercial weight-loss program (e.g. Weight Watchers). The effectiveness of these programs is difficult to assess, since programs vary widely, drop-out rates are high, and few employ members of the medical community. However, programs that emphasize realistic goals, gradual progress, sensible eating, and exercise can be very helpful and are recommended by many doctors. Programs that promise instant weight loss or feature severely restricted diets are not effective and, in some cases, can be dangerous.
For individuals who are moderately obese, medically supervised behavior modification and weight loss are required. While doctors will put most moderately obese patients on a balanced, low-calorie diet (1200500 calories a day), they may recommend that certain individuals follow a very-low-calorie liquid protein diet (40000 calories) for as long as three months. This therapy, however, should not be confused with commercial liquid protein diets or commercial weight-loss shakes and drinks. Doctors tailor these diets to specific patients, monitor patients carefully, and use them for only a short period of time.
In addition to reducing the amount and type of calories consumed by the patient, doctors will recommend professional therapists or psychiatrists who can help the individual effectively change his or her behavior in regard to eating. For individuals who are severely obese, dietary changes and behavior modification may be accompanied by surgery to reduce or bypass portions of the stomach or small intestine. Such obesity surgery, however, can be risky, and it is only performed on patients for whom other strategies have failed and whose obesity seriously threatens their health. Other surgical procedures are not recommended, including liposuction, a purely cosmetic procedure in which a suction device is used to remove fat from beneath the skin, and jaw wiring, which can damage gums and teeth and cause painful muscle spasms.
Appetite-suppressant drugs are sometimes prescribed to aid in weight loss. These drugs work by increasing levels of serotonin or catecholamine, which are brain chemicals that control feelings of fullness. Appetite suppressants, though, are not considered truly effective, since most of the weight lost while taking them is usually regained after stopping them. Also, suppressants containing amphetamines can be potentially abused by patients.
While most of the immediate side-effects of these drugs are harmless, the long-term effects of these drugs, in many cases, is unknown. Two drugs, dexfenfluramine hydrochloride (Redux) and fenfluramine (Pondimin) as well as a combination fenfluramine-phentermine (Fen/Phen) drug, were taken off the market when they were shown to cause potentially fatal heart defects.
Other weight-loss medications available with a doctor's prescription include: sibutramine (Meridia), diethylpropion (Tenuate, Tenuate dospan) mazindol (Mazanor, Sanorex) phendimetrazine (Bontril, Plegine, Prelu-2, XTrozine) and phentermine (Adipex-P, Fastin, Ionamin, Oby-trim).
Phenylpropanolamine (Acutrim, Dextarim) is the only nonprescription weight-loss drug approved by the FDA, but in November, 2000, the FDA announced that it was considering withdrawing its approval. These over-the-counter diet aids have been found to increase the risk of hemorrhagic stroke (bleeding into the brain or into tissue surrounding the brain) in women, and men may also be at risk.
Combined with diet and exercise and used only with a doctor's approval, prescription anti-obesity medications enable some patients to lose 10% more weight than they otherwise would. Most patients regain lost weight after discontinuing use of either prescription medications or nonprescription weight-loss products. Prescription medications or over-the-counter weight-loss products can cause: constipation, dry mouth, headache, irritability, nausea, nervousness, and sweating. None of them should be used by patients taking monoamine oxidase inhibitors (MAO inhibitors).
Doctors sometimes prescribe fluoxetine (Prozac), an antidepressant that can increase weight loss by about 10%. Weight loss may be temporary and side effects of this medication include diarrhea, fatigue, insomnia, nausea, and thirst.
Weight-loss drugs currently being developed or tested include ones that can prevent fat absorption or digestion; reduce the desire for food and prompt the body to burn calories more quickly; and regulate the activity of substances that control eating habits and stimulate overeating.
In April, 1999, the U.S. Food and Drug Administration (FDA) approved Xenical (orlistat), which works in the intestines, where it blocks some fat from being absorbed. This undigested fat is then eliminated in the patient's bowel movements. Available only with a doctor's prescription, many gastrointestinal side-effects can occur with Xenical. This medication should not be used by patients who have problems absorbing food or have gallbladder problems.
The Chinese herb ephedra (Ephedra sinica), combined with caffeine, exercise, and a low-fat diet in physician-supervised weight-loss programs, can cause at least temporary weight loss. However, the large doses of ephedra required to achieve the desired result can also produce serious side effects including chest pain, myocardial infarction, hepatitis, stroke, seizures, psychosis, and death. Mixing this with caffeine (a diuretic) also promotes dehydration, which can cause a number of other health problems. Ephedra should not be used by anyone with a history of diabetes, heart disease, or thyroid problems.
Getting the correct ratios of protein, carbohydrates, and good-quality fats can help in weight loss via enhancement of the metabolism. Support groups that are informed about healthy, nutritious, and balanced diets can offer an individual the support he or she needs to maintain this type of eating regimen.
As many as 85% of dieters who do not exercise on a regular basis regain their lost weight within two years. In five years, the figure rises to 90%. Repeatedly losing and regaining weight (yo-yo dieting) encourages the body to store fat and may increase a patient's risk of developing heart disease. The primary factor in achieving and maintaining weight loss is a life-long commitment to regular exercise and sensible eating habits.
Health care team roles
Physicians diagnose obesity and prescribe drugs to control it, but others can also play a role in treatment. Nutritionists and dietitians design effective and safe meal plans while taking into account the person's individual needs. Registered nurses also make nutritional recommendations and monitor the person's daily dietary intake.
Many obese people with back or knee problems cannot exercise, exacerbating the weight problem. Physical therapists design exercise programs for these individuals to improve the body's physical functionality, so more exercise can be done at higher levels of intensity. Personal trainers and fitness instructors help with weight training and cardiovascular exercise, to increase the amount of lean muscle mass and decrease body fat.
Since obesity often causes self-esteem problems, psychiatrists and psychologists use therapies including hypnotism and imagery to help improve a person's emotional well being or body image. Psychologists prescribe drugs to treat depression and anxiety disorders resulting from obesity. Treatments such as sound therapy, relaxation, and yoga, monitored by holistic health professionals, also may be helpful.
Obesity experts suggest that a key to preventing excess weight gain is monitoring fat consumption rather than counting calories, and the National Cholesterol Education Program maintains that only 30% of calories should be derived from fat. Only one-third of those calories should be contained in saturated fats (the kind of fat found in high concentrations in meat, poultry, and dairy products).
Because most people eat more than they think they do, keeping a detailed food diary is a useful way to assess eating habits. Eating three balanced, moderate-portion meals a dayith the main meal at mid-days a more effective way to prevent obesity than fasting or crash diets.
Exercise increases the metabolic rate by creating muscle, which burns more calories than fat. When regular exercise is combined with regular, healthful meals, calories continue to burn at an accelerated rate for several hours.
Finally, encouraging healthful habits in children is a key to preventing childhood obesity and the health problems that follow in adulthood.
Body Mass Index (BMI) way of computing an individual's relative weight to height ratio, used in determining the degree to which an individual may be overweight.
Obesityn abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight.
HCF Nutrition Research Foundation, Inc. P.O. Box 22124, Lexington, KY 40522. (606) 276-3119.
National Institute of Diabetes and Digestive and Kidney Diseases. 31 Center Drive, USC2560, Building 31, Room 9A-04, Bethesda, MD 20892-2560. Phone: (301) 496-3583. Website: <<a href="http://www.niddk.nih/gov">http://www.niddk.nih/gov>.
National Obesity Research Foundation. Temple University, Weiss Hall 867, Philadelphia, PA 19122.
The Weight-Control Information Network. 1 Win Way, Bethesda, MD 20896665. Phone: (301) 951120. Website: <<a href="http://www.navigator.tufts.edu/special/win.html">http://www.navigator.tufts.edu/special/win.html>.
U.S. Department of Health and Human Services. Centers for Disease Control and Prevention and National Center for Health Statistics. Prevalence of Overweight and Obesity Among Adults in the United States; Prevalence of Overweight Among Children and Adolescents: United States, 1999. Hyattsville, MD: Division of Data Services, pp. 20782003.
U.S. Food and Drug Administration. Center for Drug Evaluation and Research. <<a href="http://www.fda.gov/cder/index.html">http://www.fda.gov/cder/index.html>.
U.S. Food and Drug Administration. "Dietary Supplements Containing Ephedrine Alkaloids." 21 CFR Part 111, Docket No. 95N-0304, RIN 0901-AA59.
Obesity (Encyclopedia of Food & Culture)
OBESITY. Obesity and overweight now affect more than 50 percent of adult Americans. Diabetes mellitus, hypertension, heart disease, gallbladder disease, and some forms of cancer result from obesity. Whether these diseases are yet present or not, the obese individual should be encouraged to lose weight by appropriate methods to reduce the future likelihood that they will develop. Methods of weight loss include diet, nutritional education, self-help groups, and behavioral change. Under some circumstances drugs or surgery may be considered.
Definition and Measurement of Obesity
Obesity and overweight are best defined using the body mass index (BMI). This index is determined by dividing body weight in kilograms by the square of the height in meters: BMI = W/H2. The normal rate for BMI is 18.5 to 25. A BMI between 25 and 30 kg/m2 is defined as over-weight and a BMI above 30 kg/m2 is defined as obesity (Table 1). Visceral fat can be used as an index of central adiposity. An increase in visceral fat reflects central obesity and increases health risks. The waist circumference is used to assess the amount of visceral obesity. A waist circumference in men of 40 inches (102 cm) or more, and in women, of 35 inches (88 cm) or more, is the threshold for defining central obesity (Table 1).
Prevalence of Overweight
More females than males are overweight at any age. The frequency of overweight increases with age to reach a peak at forty-five to fifty-four years in men and at age fifty-five to sixty-four in women. The National Health and Nutrition Examination Survey (NHANES) conducted by the U.S. government (published in 1993) found a BMI of 25 or more in 59.4 percent of men age twenty years or older and in 50.7 percent of women over the age of twenty years. The prevalence of obesity (BMI 30 or more) was 19.5 percent in men and 25.0 percent in women. The incidence of obesity continues to increase dramatically in the United States and elsewhere. A number of factors including age, sex, and physical inactivity influence the amount of body fat.At birth, the human infant contains about 12 percent body fat. During the first years of life, body fat rises rapidly to reach a peak of about 25 percent by six months of age and then declines to 18 percent over the next ten years. At puberty, there is a significant increase in the percentage of body fat in females and a decrease in males. By age eighteen, males have approximately 15 to 18 percent body fat, and females have 25 to 28 percent. Between
|Classification of overweight and obesity by BMI, waist circumference, and associated disease risk|
|Disease risk* relative to normal weight and waist circumference|
|BMI kg/m2||Obesity class||Men = 102 cm (= 40 in) Women = 88 cm (= 35 in)||>102 cm (>40 in) >88 cm (>35 in)|
|35.09.9||II||Very High||Very High|
|Extreme Obesity||= 40||III||Extremely High||Extremely High|
*Disease risk for type 2 diabetes, hypertension, and CVD.
+Increased waist circumference can also be a marker for increased risk even in persons of normal weight.
Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adultshe Evidence Report. National Institutes of Health.
Obes Res 1998;6 Suppl 2:51S09S.
ages twenty and fifty, the fat content of males approximately doubles and that of females increases by about 50 percent. Total body weight, however, rises by only 10 to 15 percent: fat now accounts for a larger part of the body weight and lean body mass decreases.
Risks Related to Obesity
As the BMI increases, there is a curvilinear rise in excess mortality. This excess mortality rises more rapidly when the BMI is above 30 kg/m2. A BMI over 40 kg/m2 is associated with a further increase in overall risk and for the risk of sudden death. The principal causes of the excess mortality associated with overweight include hypertension, stroke, and other cardiovascular diseases, diabetes mellitus, certain cancers, reproductive disorders, gall-bladder disease, and sudden death.
The insulin-resistant state or metabolic syndrome is strongly associated with visceral fat. It may include consequences such as glucose intolerance or type 2 diabetes mellitus, hypertension, polycystic ovarian syndrome, dyslipidemia (the state of abnormalither higher or loweralues for blood fats), and other disorders. These are often responsive to weight loss, especially when this is achieved early and the loss is maintained.
Development of Obesity
Several mechanisms lead to obesity, including neuroendocrine imbalances, particular drugs, diet, reduced energy expenditure, and genetic factors that lead to certain syndromes and predisposition to obesity. Obesity can follow damage to the hypothalamus in the brain, but this is rare. Cushing's disease is somewhat more common and can result in obesity. Treatment should be directed at the cause of the increased formation of adrenal corticosteroids.
Treatment of diabetics with insulin, sulfonylureas, or thiazolidinediones (but not metformin) can increase hunger and food intake, resulting in weight gain. Treatment with some antidepressants, anti-epileptics, and neuroleptics can also increase body weight, as can cyproheptadine (a serotonin antagonist that produces weight gain), probably through effects on the monoamines (including norepinephrine, epinephrine, dopamine, histamine, and serotonin) in the central nervous system.
Eating a high-fat diet and excessive consumption of sugar-sweetened beverages and the prevalence of abundant varieties of food in cafeterias or supermarkets are dietary factors in the development of obesity. Reduced energy expenditure relative to energy intake is another major component. Energy expenditure can be divided into four parts.
An inactive individual at rest burns between 800 and 900 kilocalories during a twenty-four hour period. This rate is lower in females than in males, and declines with age, and could account for much of the increase in fat stores if food intake does not decline similarly. The effect of physical exercise on metabolism is variable but on average is responsible for about one-third of the daily energy expenditure. From a therapeutic point of view this component of energy expenditure is most easily manipulated. Dietary thermogenesis is the energy expenditure that follows the ingestion of a meal. Heat produced by eating may dissipate up to 10 percent of the ingested calories. These thermic effects of food are one type of metabolic "inefficiency" in the body, that is, where dietary calories are not available for "useful" work. In the obese, the thermic effects of food are reduced particularly in individuals with impaired glucose tolerance or diabetes. Acute over-or underfeeding will produce corresponding shifts in overall metabolism, which can be as large as 15 to 20 percent.
Genetic factors can produce some types of obesity that are easily recognized. Among these types of obesity are: (1) the Bardet-Biel syndrome, characterized by retinal degeneration, mental retardation, obesity, polydactyly, and hypogonadism; (2) the Alstrom syndrome, characterized by pigmentary retinopathy, nerve deafness, obesity, and diabetes mellitus; (3) Carpenter syndrome, characterized by acrocephaly (abnormalities in the facial and head bones), mental retardation, hypogonadism, obesity, and preaxial syndactyly (extra fingers or toes on one hand or foot); (4) the Cohen syndrome, characterized by mental retardation, obesity, hypotonia (reduced tone of the muscles, resulting in a "floppy" muscle mass), and characteristic facies (an appearance of the face that is typical of specific genetic diseases); (5) the Prader-Willi syndrome, characterized by hypotonia, mental retardation, hypogonadism, and obesity; and (6) the pro-opiomelanocortin (POMC) syndrome, characterized by defective production of POMC that is recognized as a red-headed fat child with a low plasma cortisol (a value that is below the normal range).
If both parents are obese, about 80 percent of their offspring will be obese. If only one parent is obese, the likelihood of obesity in the offspring falls to less than 10 percent. Studies with identical twins suggest that inheritance accounts for about 70 percent and environmental factors (diet, physical inactivity, or both) account for 30 percent of the variation in body weight. Deficiency of the gene leptin and deficiency of the leptin receptor are rare, but are associated with massive human obesity. Absence of convertase I has also been associated with obesity in one family. The most common defects associated with massive obesity are abnormalities in the melanocortin receptor systemp to 4 percent of massively obese people may have this type of defect.
Evaluation of the Obese Patient
A medical evaluation should include the expected medical history, family history, personal and social history, and review of the systems of the body with a particular focus on the medications that can cause weight gain. A physical examination should include an assessment of the patient's height, weight, waist circumference, blood pressure, and level of health risk due to obesity. Laboratory tests should include a lipid panel, glucose level, chemistry panel for hepatic (liver) function and uric acid, thyroid function testing, and, if indicated a cortisol level.
Evaluating Risk Using the Body Mass Index (BMI)
Individuals with a normal BMI (205 kg/m2) have little or no risk from obesity. Any individual in this weight range who wishes to lose weight for cosmetic reasons should do so only with conservative methods. Individuals with a BMI of greater than 25 to 29.9 kg/m2 are in the low-risk group for developing heart disease, hypertension, gallbladder disease, and diabetes mellitus associated with obesity. They too should be encouraged to use low-risk treatments, such as caloric restriction and exercise. Individuals with a BMI of 27 to 30 kg/m2 or more who have diseases related to obesity may use adjunctive pharmacotherapy for weight loss.
Individuals with a BMI of 30 to 40 kg/m2, have moderate risk for developing diseases associated with obesity. Diet, drugs, and exercise would all appear to be appropriate forms of treatment. Individuals with significant degrees of excess weight often find exercise difficult. However, exercise is very important in helping to maintain weight loss. The use of weight loss medications, as an adjunct to treatment, may also be useful in this group. Individuals who have a BMI above 40 kg/m2 have a high risk of developing diseases associated with their obesity. Moderate to severe restriction of calories is the first line of treatment, but for some of these patients surgery may be advisable.
Treatment of Obesity
Any diet must reduce an individual's caloric intake below daily caloric expenditure if it is to be successful. This requires an assessment of caloric requirements, by estimating caloric expenditure from desirable weight tables; for men, multiply desirable weight by 30 to 35 kilocalories/kilogram, (146 kilocalories/lb.); for women, multiply desirable weight by 25 to 30 kilocalories/kilogram (124 kilocalories/lb.). After assessing caloric requirements, a reasonable calorie deficit can be prescribed. A caloric deficit of 500 kilocalories/day (3,500 kilocalories/week) will produce the loss of approximately one lb. (0.45 kilograms) of fat tissue each week. Table 2 gives a list of diets divided into different levels of energy.
The very low calorie diet (below 800 kilocalories) was developed to facilitate the rate of weight loss since lower energy intake should lead to greater energy deficit. In free living people, however, diets with 400 kilocalories/day have not produced greater weight loss than those with 800 kilocalories/day, suggesting either that they are harder to adhere to or that there is an adaptation in energy expenditure. In either case, these diets should only be used under appropriate medical supervision.
|Characterization of diets by composition|
|Type of diet||Calories||Fat g (%)||Carbohydrate g (%)||Protein g (%)|
|Typical American||2,200||85 (35)||274 (50)||82 (15)|
|High-fat, low carbohydrate||1,400||94 (60)||35 (10)||105 (30)|
|Moderate-fat||1,450||40 (25)||218 (60)||54 (15)|
|Low & very low fat||1,450||164 (105)||23571 (655)||542 (150)|
Types of diets. There are several types of diets with more than 800 kilocalories/day that usually have more than 1,200 kilocalories/day. They can be divided into several categories. These categories are based on the relative proportion of macronutrients included in the diet and whether they use special foods. For all diets it must be true that they reduce the calorie intake to produce a negative energy balance. Low-carbohydrate diets are touted because they produce ketosis (a state of increased ketones associated with diabetes and fasting) and allow you to eat all of the protein and fat you want. This ends up reducing total calorie intake to about 1,500 kilocalories/day. Since these diets generally have carbohydrate levels below 50 g./day they are ketogenic and can be monitored clinically by the appearance of ketones in the urine. They vary in the level of fiber that is employed. The Atkins diet has low fiber levels, the Sugar Busters diet higher fiber levels.
Low-fat diets recommend fat intake in the range of 10 to 20 percent of calories. The higher carbohydrate increases fiber intake. These diets were developed in a setting designed to reverse the atherosclerotic plaques associated with risks for heart disease, but because of the high fiber content they were often associated with weight loss. Moderate fat levels with higher carbohydrates are characteristic of many widely recommended "healthy diets." For weight loss, the New York Health Department recommends the Prudent Diet, which has stood the test of time.
The portion-controlled diet makes use of prepared foods that have a narrow range of calories. This includes liquid or powdered drinks as well as frozen or canned entrees that have about 300 kilocalories/meal. These can be combined conveniently and thus removes the problem of counting calories from the individual. A number of popular diets focus on a single food, and although nutritionally unbalanced, they are simple to follow and the monotony of single items tends to limit food intake.
Food Guide Pyramid. The Food Guide Pyramid provides an approach to evaluating the quality of your diet. At the bottom of the pyramid are the grains, beans, and starchy vegetables that provide vitamins, minerals, fiber, and energy; six or more servings are recommended. On the next level are the vegetables (3 servings) and the fruits (3 servings). On the third level are the meats, fish, poultry, and nuts (2 servings) along with the milk and yogurt (2 servings). At the top are the fats, sweets, and alcohol. Reducing the number of servings proportionally will provide you with a calorie-reduced diet. Most important for the dieter, however, is to sharply reduce the fats and sugar at the top of the pyramid and to reduce or eliminate alcoholic beverages. Not only do alcoholic beverages have calories, their consumption tends to reduce the individual's control in selecting the quality and quantity of foods to eat.
Changing behavioral patterns of eating. The basic principles of behavioral approaches for obesity can be summarized under the ABCs of eating.
- The A stands for antecedent. If one looks at eating as the response to events in the environment, then the antecedent events are those that trigger eating.
- The B stands for the behavior of eating. This includes among other things the place, the rate, and the frequency with which an individual eats. If the act of eating can be focused at one place with one plate and place setting it can help to provide control over eating.
- The C is the consequence of the eating. The feelings an individual has about eating can be altered, and rewards for changing eating patterns can be instituted.
Exercise and physical activity. The only part of energy expenditure that is amenable to significant manipulation is physical activity. During sleep, the lowest level of activity, approximately 0.8 kilocalories/minute is consumed. Thus, if an individual sleeps for an entire 24 hours, approximately 1,150 calories will be expended. Reclining increases this level to approximately 1.0-1.4 kilocalories/minute. Obese and diabetic patients should be encouraged to increase their physical activity for two reasons: First, it consumes calories, but second, and more important, exercise increases glucose utilization and may improve insulin sensitivity.
Drug treatment of obesity. Only a few drugs have been approved by the Food and Drug Administration for treatment of obesity. Studies following individuals who have used these drugs for two years have been published for sibutramine (Meridia) and orlistat (Xenical). Weight-loss drugs should be reserved for patients with moderate-or high-risk obesity (BMI >30 kg/m2) or a BMI above 27 if they have other significant diseases related to obesity. They should be considered for the patient who has failed to lose weight with other methods. Herbal products containing ephedra and an herbal source of caffeine can also produce weight loss when used in accordance with the package instructions.
Surgery. Gastric operations reduce the size of or bypass the stomach, but should be reserved for people with a BMI above 40 or when recommended by a physician.
The Obese Child
Estimates of the prevalence of obesity in children range from 3 to 15 percent. This figure has been rising more rapidly than in the rest of the population. The appearance of obesity in childhood and particularly adolescence is important because it most often persists into adult life. It may be a precursor to the appearance of type 2 diabetes in adolescents. The possibility of treatment should be considered for children who are above the seventy-fifth percentile of weight for height, and might be encouraged for those who are above the ninety-fifth percentile of weight for height. The treatment of prepubertal children should probably involve both parents and child since at this age the principal control of food availability is in the hands of the parents. For adolescents, however, it may be better to separate patient and parents, since the interaction between these groups may be part of the problem. Where growth has not reached its fullest extent, dietary restriction should attempt to reduce further weight gain. Severe caloric restriction and the use of appetite-suppressing drugs may slow height growth. For both children and adolescents, involvement in a regular exercise program is probably the first line of treatment.
See also Anorexia, Bulimia; Body; Body Composition; Caloric Intake; Eating: Anatomy and Physiology of Eating; Fasting and Abstinence; Fats; Fiber, Dietary; Hunger, Physiology of.
Bessesen, D. H., and R. Kushner. Evaluation and Management of Obesity. Center for Obesity Research and Education. Philadelphia: Hanley and Belfus, 2002.
Bray, George A. Contemporary Diagnosis and Management of Obesity. Newtown, Pa.: Handbooks in Health Care, 1998.
National Heart, Lung, and Blood Institute (NHLBI). Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Bethesda, Md., 1998.
Yanovski, J., and S. Z. Yanovski. "Obesity." New England Journal of Medicine 346, no. 8 (21 February 2002): 59102.
Obesity (Encyclopedia of Drugs, Alcohol, and Addictive Behavior)
This term derives from the Latin (obesus, meaning "to eat up"), and it came into use in English in the early 1600s to mean a condition characterized by excessive bodily fat. Excess body weight is associated with the increased storage of energy in the form of adipose tissue. Standard criteria for obesity are (1) greater than 20 percent above ideal body weight (IDW) for a given height, as determined from actuarial tables, or (2) body mass index (BMI), defined as weight in kilograms divided by height in meters squared (kg ÷ m2 = BMI), greater than 27 for men and greater than 25 for women.
Obesity represents the upper end of a bodyweight continuum, rather than a qualitatively different state. Obesity can derive from a variety of causes, but a significant genetic contribution has been demonstrated.
Being overweight to a statistically significant above-average degree or having proportionately more body fat than average is believed to be due primarily to genetic factors that influence appetite, metabolism, and activity levels. Most notably, obesity is more prevalent (ten times more likely) in persons whose parents, brothers, or sisters are obese. Studies in identical twins have clearly demonstrated that genetics plays a major role. For example, nonidentical twins raised together were less similar in weight than identical twins raised apart.
Beyond the genetic component, researchers have been examining the role of hormones, most specifically leptin, a hormone secreted by fat tissue that affects the brain's appetite control centers. In some studies, mice given injections of leptin lost their appetites and, consequently, lost weight. The human response to leptin varies dramatically, and the relationship between plasma leptin levels and obesity in humans is not yet clear or confirmed. According to one study, mutations in the leptin gene are indeed responsible for obesity in both mice and humans, but these mutations are quite rare outside of the laboratory setting. Another study shows that leptin is a signal to the hypothalamus of peripheral fat deposits, but further studies are being conducted to determine if obese individuals have trouble with leptin access into the brain. Other researchers have found that lean, physically active men have lower levels of leptin than heavier, sedentary men (ages 47 to 83).
Leptin research continues since solid findings could help in the treatment and prevention of obesity and diseases and health problems linked to obesity, such as hypertension, stroke, and type 2 diabetes (diabetes mellitus).
The prevalence of obesity (in this case defined as having body fat in excess of 25% for males or 30% in females) varies remarkably across ethnic groups and cultures, and across age groups. In the United States, obesity is consistently less common among African-American men than among white men across the entire age range; is consistently more common among African-American women than among white women; and tends to be more common among women of Eastern European and Italian ancestry than among those of British ancestry. Socioeconomic factors affect the prevalence of obesity, but men and women are affected differently: It is more common among all women in lower socioeconomic groups, but men in lower socioeconomic groups are leaner than average. Overall, approximately 40 million Americans are obese.
Some researchers and clinicians see similarities among certain patterns of overeating and other excessive behaviors such as drinking too much ALCOHOL, compulsive GAMBLING, engaging in "too much" sexual activity, and even exercising compulsively. Although there may be such similarities, the semantics attached to problems of overeating and OBESITY are formidable.
Not all persons whose weight is above average are obese (they may have excess muscle mass); not all who are obese eat excessively; not all who eat excessively become obese; and some individuals who have clinically recognized disorders centered on eating and body weight, such as BULIMIA, may or may not be obese.
(SEE ALSO: Bulimia Nervosa; Overeating and Other Excessive Behaviors)
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TIMOTHY H. MORAN
REVISED BY REBECCA MARLOW-FERGUSON