The global obesity problem

A person has traditionally been considered to be obese if they are more than 20 percent over their ideal weight. That ideal weight must take into account the person's height, age, sex, and build.
Obesity has been more precisely defined by the National Institutes of Health (the NIH) as a BMI of 30 and above. (A BMI of 30 is about 30 pounds overweight.)
The BMI (body mass index), a key index for relating body weight to height, is a person's weight in kilograms (kg) divided by their height in meters (m)squared. Since the BMI describes the body weight relative to height, it correlates strongly (in adults) with the total body fat content. Some very muscular people may have a high BMI without undue health risks. 
Obesity is often multifactorial, based on both genetic and behavioral factors. Accordingly, treatment of obesity usually requires more than just dietary changes. Exercise, counseling and support, and sometimes medication can supplement diet to help patients conquer weight problems. Extreme diets, on the other hand, can actually contribute to increased obesity.Overweight is a significant contributor to health problems. It increases the risk of developing a number of diseases including:Type 2 (adult-onset) diabetes
High blood pressure (hypertension)
Stroke (cerebrovascular accident or CVA)
Heart attack (myocardial infarction or MI)
Heart failure (congestive heart failure)
Cancer (certain forms such as cancer of the prostate and cancer of the colon and rectum) 
Gallstones and gall bladder disease (cholecystitis)
Gout and gouty arthritis
Osteoarthritis (degenerative arthritis) of the knees, hips, and the lower back
Sleep apnea (failure to breath normally during sleep, lowering blood oxygen)
Pickwickian syndrome (obesity, red face, underventilation, and drowsiness).