Obesity is a complicated disease. It is not simply a bad habit. It has life-threatening implications and a substantial impact on health and economic and social well-being.
It is not entirely clear why some people are obese and others are not. Many people who maintain a normal weight eat in an entirely unconstrained way; many who are obese eat cautiously yet still have difficulty losing weight even with careful dieting. For many obese people the problem is not simply the result of over-eating or under-activity.
Obesity is an extraordinarily complex disease associated with metabolic, neurochemical, and endocrine abnormalities, as well as environmental and social determinants. Some patients have a variety of abnormalities in how food and calories are processed and metabolized. It is likely also that the regulatory systems that control food intake and the recognition of hunger and satiety are defective in obese people. These regulatory systems probably function by controlling a number of biological processes, including the activity of certain hormones, neuro-chemicals, and the metabolism of individual cells. Abnormalities in any part of the regulatory systems contribute either to the cause of obesity or to sustaining it and making it more difficult to control.
Behavioral, psychological and emotional factors probably do not cause obesity and probably do not cause the metabolic regulators to reset or malfunction. Rather, these factors appear to have a major role in affecting each person's ability to superimpose willful control on the faulty body weight regulators and in sustaining that control for the continuing task of maintenance. Losing weight and maintaining a normal weight depend on making adjustments in eating patterns and in sustaining efforts to enable each individual to override the faulty regulators.
Traditional therapy has depended primarily on lowering calorie intake, but this approach, used alone, fails to recognize the abnormal metabolic-regulatory functions. It has tended to view obesity simply as a bad habit or, more often, as a character disorder with serious psychological implications. This narrowly focused analysis shifts all of the responsibility for therapy to the patient. The traditional judgmental approach assumes that the patient is to blame for the disease, particularly if the therapy is not successful.
Obesity can be controlled, but it cannot be cured. We now know that weight loss can be achieved, weight control is realistic, and long-term maintenance is possible. As we continue to better understand the disease, with this understanding will come a more sophisticated approach to its management.