Definition of Obesity and Indications for Surgery

Obesity is an excess of body fat that frequently results in a significant impairment of health. It is a chronic, lifelong, genetically related, life-threatening disease of excessive fat storage. Obesity results when the size or number of fat cells in a person’s body increases. A normal-sized person has 30 to 35 billion fat cells. When a person gains weight, these fat cells first increase in size and later in number. One pound of body fat represents about 3,500 calories. The prevalence of overweight and obesity in the United States make obesity a leading public health problem that can have medical, social, psychological, and economic consequences. Obesity is growing at an exponential rate: It is estimated that there are more than 150,000 bariatric operations performed each year in the United States.

Although “overweight” technically refers to an excess of body weight and “obesity” to an excess of fat, these two words can be defined operationally in terms of body mass index. The body mass index (BMI) is the most practical way to evaluate the degree of obesity, although it does not take into account the different ratios of adipose to lean tissue. Visceral fat (or central obesity) has a much stronger correlation with certain diseases, such as cardiovascular disease, than the BMI alone. The absolute waist circumference (>102 cm in men and >88 cm in women) or waist-hip ratio (> 0.9 for men and > 0.85 for women) are both used as measures of central obesity.