Author(s): John K DiBaise [*] 2 , Amy E Foxx-Orenstein 1
bariatric surgery; gastroenterologist; complications; endoscopy; obesity; pathogenesis; treatme; weight loss
Obesity is a problem of epidemic proportions in the United States and worldwide. About two-thirds of adults in the United States are overweight or obese, while over a third is obese  . Obesity is a well-known risk factor for many conditions including hypertension, hyperlipidemia, diabetes mellitus, coronary artery disease, stroke, osteoarthritis, sleep apnea and certain cancers. Obesity is also associated with premature death. Certainly, the emotional (psychological and social) effects of obesity can be significant as well. The diseases associated with obesity are responsible for a substantial amount of healthcare costs related to doctor visits, testing, treatments and hospitalizations  . Of additional concern is that obesity is becoming common in children, for children who are overweight have a greater chance of becoming obese adults. Like adults, overweight children may develop associated health problems - regardless of whether the obesity persists into adulthood  .
One of the simplest and most accepted ways to measure obesity involves calculation of the BMI. BMI was developed as an operational definition for classifying the magnitude of both obesity and malnutrition and is a determination of body fat based on weight divided by height squared  . BMI allows both a determination of health risk and a comparison of obesity between individuals. Adults with a BMI of 25-29.9 kg/m2 are considered overweight, while those with a BMI of 30 kg/m2 or more are considered obese. Obesity can be further classified as Class I, II or III depending upon the degree of increase in BMI over 30 kg/m 2 (Table 1). A BMI >40.0 kg/m2 is sometimes referred to as extreme obesity, while a BMI >50 kg/m 2 is sometimes referred to as super obesity. Although recent surveys suggest that the incidence of obesity seems to be leveling off, the incidence of extreme and super obesity continues to rise at an alarming rate  . Longitudinal data have shown J-shaped or U-shaped relationships between absolute mortality and BMI  . Importantly, although BMI is correlated with body fat in most individuals, it has limitations in delineating fat mass from fat-free mass and thus, may overestimate body fat in those with a muscular build and underestimate body fat in those who have lost muscle mass  .
The distribution of body fat also affects health. Fat stored primarily in the abdomen (i.e., visceral fat) rather than in the hips (i.e., subcutaneous fat) is associated with a higher risk for heart disease, cancer and diabetes  . Although body composition is optimally measured using dual-energy x-ray absorptiometry, computerized tomography and MRI, due to their expense and limited availability, a number of relatively simple, inexpensive and readily available methods have been devised that provide good estimations of body fat. Two such methods that have been validated against the other methods mentioned are the measurement of waist circumference and waist-hip ratio. A waist circumference of > 35 inches around or waist-hip circumference ratio > 0.80...