Simply put, obesity is a complex disease characterized by excessive body fat. The physiologic biochemical and genetic evidence is overwhelming that clinically severe obesity is not a simple disorder of will power, but a complex disease. While the biological basis is not fully understood, contributing causes include heredity, environmental, cultural, socioeconomic and psychological factors. Women are eight times more susceptible to clinically severe obesity than men. We know that "insulin resistance," the manner in which insulin is produced in the pancreas and used at the cell level is another genetic factor contributing to the disease. Adipose tissue deposition and energy efficiency also seem to be genetically based.

Genetically predisposed patients experience "over-adjustment" of metabolic rate in response to strenuous dietary efforts.

Non-genetic factors include total energy (food calories) intake, total internal and external energy used, and relative proportions of proteins, fats and carbohydrates in one's diet. Frequency and duration of physical activity patterns of leisure activity (i.e. sedentary versus active) and the amount of lean muscle mass being carried are among the non-genetic factors that determine one's predisposition to clinically severe obesity.

New research has begun to pinpoint precise genetic differences at the chromosomal level which lead to severe obesity.

Published scientific reports document that non-operative methods alone -have not been effective In achieving a medically significant, long-term weight loss in severely obese adults. To add insult to injury, diets do not work, and in fact usually compound the "yo-yo" effect. In 95 percent of cases, any weight lost through these numerous programs is back on within one to five years.

The 1991 National Institutes of Health (NIH) Consensus Development Conference Statement on the surgical treatment of obesity (NIH Consensus Report) says those who have had little success with diets or other non-surgical treatments may be considered for surgical treatment. Surgery is not necessary to cure obesity, but is sometimes medically necessary for clinically severe obesity because it offers virtually the only effective long-term method of weight control.

At what stage does obesity become clinically severe or morbid obesity? Several methods are currently in use to classify clinically severe obesity. The two most common are excess weight based on "Ideal Calculated Weight" and "Body Mass Index" (BMI).

Determining ideal calculated weight is slightly different for men and women. For both, excess weight is the amount of weight greater than the ideal calculated weight. The calculation for Ideal Calculated Weight is approximate:

Using NIH guidelines, roughly 100 pounds greater than the ideal Calculated Weight constitutes clinically severe obesity; and indicates that surgical treatment may be considered. In cases where co-morbid conditions such as diabetes, hypertension, respiratory ailments and bone and/or joint disease are severe, an excess weight even lower than 100 pounds may be considered for surgical treatment.

Body Mass Index (BMI), referenced in 1991 NIH report, and a method used by some insurance companies also indicates whether surgery is advisable. BMI is the weight in kilograms divided by the height in meters, squared. Calculate your own BMI using the form below. (Your browser must support JavaScript.)

A BMI over 40 is considered "Clinically Severe Obesity" and represents a level for which surgery should be considered. When co-morbid conditions are present a BMI of 35 or higher indicates surgery should be considered.

Successful Treatment Expectations

In general, successful treatment of clinically severe obesity requires a loss of a major portion of excess weight, improvement or cure of co-morbid conditions, and lifelong commitment. Success with respect to this operation is defined as achieving a weight within 40 pounds (or less) of ideal body weight. This usually takes place between 12 and 18 months after surgery in patients who follow the recommended diet and exercise programs. In the experience of centers across the country, over 80 percent of patients achieve this goal. Excellent weight loss is a reduction of 50 to 75 percent of excess weight

Who Is a Candidate for Surgery?

In summary, for a person to be a candidate for surgery, all of the following must be met: