Obesity is defined as having a body weight more than 30 percent above the normal body weight (Obesity). This excess weight must be in the form of fat (adipose tissue) and not excess weight due to muscle: excess muscle does not count for the weight attributed to obesity, so a body builder would not be considered obese. The causes of obesity are varied, and major causes include genetic factors, environmental factors, psychological factors, drug side effects, and some illnesses that affect weight (Kaplan). Obesity is harmful because of the medical problems it causes such as high blood pressure, cardiovascular disease, non-insulin dependent diabetes (Type II), arthritis, and cancer (Kaplan; Liebman; Obesity).
Body weight depends on the balance between the number of calories taken in, the number burned, and the excess stored as fat (Kaplan). If you consume more calories than you expend, you will gain weight as fat. Fat is stored in adipose tissue, either by enlarging the cells already there or by creating new ones. Many features of modern life promote weight gain, such as a sedentary lifestyle, not enough exercise, eating at fast food restaurants and eating oversized portions of high-calorie foods and drinks. Total metabolism is the rate at which you use energy (calories) when exercising or going about daily life. Resting energy metabolism is the rate at which you burn calories when not being physically active, and resting energy metabolism varies from person to person, and is affected by age, gender, genetic makeup, psychological state, and level of physical activity. Total and resting metabolism together determine how many calories you burn up in a day.
Several dozen genes have been identified which are associated with obesity in humans (Kaplan). The strength on the influence of genetic factors on obesity varies significantly from one person to another. Although it is impossible to determine the exact influence, it can...