I think health risks associated with obesity are the most common in America. People do not get enough activity, and we eat too much salty, fatty foods. This can lead to all kinds of health risks including cancer and heart disease.
The most common avoidable,preventable or treatable health risk factors are the following:
Smoking, Hypertension (elevated blood pressure), Diabetes, Obesity and Alcoholism.
There are also genetic factors about which nothing can be done.
For the avoidable factors, they are listed roughly in order of risk.
In the U.S., physical inactivity and unhealthy diet are the highest behavioral risk factors for non-communicable diseases. Most people consume diets that are high in simple carbohydrates, refined sugars and processed snacks. They may also consume an excessive amount of saturated fat. The typical American diet lacks a balance of complex carbohydrates, protein and vegetables. The risks associated with an improper diet increase with lack of physical activity. Most people in the industrialized world live relatively sedentary lives. Exercising regularly is difficult for those whose work does not require physical exertion.