Obesity means accumulation of excess fat on the body. Obesity is considered a chronic (long-term) disease, like high blood pressure or diabetes. It has many serious long-term consequences for your health, and it is the second leading cause of preventable deaths in the United States (tobacco is the first). Obesity is defined as having a body mass index (BMI) of greater than 30. The BMI is a measure of your weight relative to your height. See medicine's Body Mass Index Calculator.

Obesity occurs over time when you eat more calories than you use. The balance between calories-in and calories-out differs for each person. Factors that might tip the balance include your genetic makeup, overeating, eating high-fat foods and not being physically active. is a condition in which the natural energy reserve, stored in the fatty tissue of humans and other mammals, is increased to a point where it is associated with certain health conditions or increased mortality.

Causes of obesity

Obesity tends to run in families, suggesting a genetic link. Yet families also share common dietary, physical exercise, attitude and lifestyle habits that may also contribute to obesity. Separating these from purely genetic factors is not an easy statistical or diagnostic task.

During pregnancy a woman's weight necessarily increases. 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.

In less than one out of every 100 cases, there is a medical reason for obesity. Conditions such as Cushing's syndrome (over-production of steroid hormones in the body) and an under-active thyroid gland are rare causes of weight gain.

Genes affect a number of weight-related processes in the body, such as metabolic rate, blood glucose metabolism, fat-storage, hormones, to name but a few. Also, some studies of adopted children indicate that adopted children tend to develop weight problems similar to their biological, rather than adoptive, parents.

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.

Treatment for Obesity

For most people who are overweight or obese, the safest and most effective way to lose weight is to eat less and exercise more. If you eat less and exercise more, you will lose weight. It is as simple as that. There are no magic pills. Diets that sound too good to be true are just that.

Achieving a healthy weight is usually done through dietary changes, increased activity and behavior modification. Depending on your situation, your doctor may suggest prescription medication or weight-loss surgery to supplement these efforts.

Orlistat (Xenical) is a medication that blocks the absorption of dietary fat and is also approved for longer-term use. However, it causes unpleasant side effects (greasy stool), and you also need to supplement your diet with fat-soluble vitamins.

Lifestyle modifications such as increasing physical activity and decreasing calorie intake are recommended instead of "dieting." Crash diets should definitely be avoided. The best approach to changing your diet is to talk to your doctor to find out what is best for you. Your doctor can provide you with dietary guidelines or refer you to a dietician for further help. Dietary guidelines will differ for each person depending on height, weight, concurrent health conditions, and desired amount of weight loss.

Although surgery (such as gastric bypass) is the last resort for the treatment of obesity, it can be extremely effective. However, it should be performed at an experienced surgical center, because such operations can carry significant risks, especially in the post-operative period.