What are the main substances that can make a calorie surplus, and the mechanism by which they can fatten?
The mechanism for the formation of fat is called Lipogensis. When more calories are taken in than used up through metabolism and exercise the body stores the excess energy as a glucose polymer called glycogen. When glycogen storage is full and caloric intake still exceeds expenditures then excess food is stored as fat. Insulin an enzyme produced by the pancreas plays a key role in controlling blood sugar levels and fat formation or lipogenesis.
The energy in food is consumed and used by the body through a process called respiration. In this multi-step process glucose is converted through glycolysis into two Pyruvate molecules, they are them converted into two Acetyl CoA molecules, which; are oxidized in the mitochondria of cells to produce Carbon dioxide and 36 ATP molecules. Adenosine triphosphate (ATP) is useful energy source for all cellular processes.
Lipogensis begins similar to respiration in that food/glucose is converted into Acetyl CoA, however; instead of being oxidized Acetyl CoA is reduced with the energy from ATP and the addition of hydrogen to form fatty acids.
Calories function in one of two ways. If the individual consumes lots of calories and fails to burn those through body function and exercise, the calories will turn to fat usually in the abdomen, butt, and arm region. The human body will take the extra energy and store it as fat. If, however, you burn (through body maintenance--your body will use the extra energy to rebuild and repair the body) and exercise) more calories than you consume, you body will increase in lean body mass and muscle. That’s why exercise is crucial to losing weight. Building muscle creates lean body mass, and your body has to burn more calories to maintain the lean muscle mass.