Obesity, in simple terms, is having a high proportion of body fat. Fat is important for storing energy and insulating your body, among other functions. The human body can handle carrying some extra fat, but beyond a certain point body fat can begin to interfere with your health. For this reason, obesity is more than a cosmetic concern. Obesity puts you at greater risk of developing high blood pressure, diabetes and many other serious health problems. One in three Americans are obese.

Modest weight loss can improve or prevent complications associated with obesity. Weight loss is usually possible through dietary changes, increased physical activity, and behavior modification. For people who don’t respond to these lifestyle changes, other more involved obesity treatments are available to enhance weight loss. These include prescription medications and weight-loss surgery.

Although there are genetic and hormonal influences on body weight, ultimately excess weight is a result of an imbalance of calories consumed versus calories burned through physical activity. If you consume more calories than you expend through exercise and daily activities, you gain weight – your body stores calories that you don’t need for energy as fat. The following are several acknowledged factors — usually working in combination — which can contribute to weight gain and obesity:

  • Diet: Regular consumption of high-calorie foods, such as fast foods, or increasing their portion sizes contributes to weight gain. High-fat foods are dense in calories. Loading up on soft drinks, candy and desserts also promotes weight gain. Foods and beverages like these are high in sugar and calories. In general, eating away from home also increases calorie intake.

  • Inactivity: Sedentary people are more likely to gain weight because they don’t burn calories through physical activities.

  • Pregnancy: During pregnancy a woman’s weight tends to increase. Some women find this weight difficult to lose after the baby is born. This weight gain may contribute to the development of obesity in women.

  • Medical problems: Uncommonly, obesity can be traced to a medical cause, such as low thyroid function or excess production of hormones by the adrenal glands (Cushing’s syndrome). A low metabolic rate is unlikely to cause obesity. In addition, it’s unclear whether polycystic ovarian syndrome contributes to obesity. Some medical problems, such as arthritis, can lead to decreased activity, which may result in weight gain.