PHILADELPHIA -- Exercise and diet play an important role in weight regulation, but the true key to weight control lies in understanding and identifying personal quirks in the biological system.
Researchers examining the function of hormones such as leptin and their ability to influence the systems that control body weight are beginning to understand how genetic and biological factors influence a person's propensity toward obesity.
And in future years, physicians may be able to detect such predisposition and treat obesity with tailored drug treatments.
"While some people are born to become obese, most people experience weight gain because of a slight abnormality in their weight regulation system. These abnormalities make individuals more susceptible to the impact of factors like diet and exercise that, over a period of years, can strongly influence body weight gain," explained Dr. Michael W. Schwartz, associate professor of medicine at the University of Washington School of Medicine and Puget Sound Veterans Affairs Health Care System in Seattle.
Schwartz discussed the role of leptin and the nervous system on body weight during a news briefing, "Obesity Update: Molecular Biology of Energy Regulation and Implications for Treatment and Public Policy," Feb. 12 at the 1998 meeting of the American Association for the Advancement of Science in Philadelphia.
Schwartz and fellow researchers have investigated the role of neuropeptides in the brain as mediators of the action of leptin, a hormone known to limit food intake and body weight by acting on the central nervous system. Their studies have identified brain circuits that translate the leptin signal to a change in appetite. Such findings indicate that some people may become obese due to difficulties receiving bloodborne messages that tell their brain to reduce food intake or burn off excess weight.
Schwartz likened the control of body weight to that of blood pressure. Just as blood pressure works to stay constant in response to different activities and stimuli, a person's weight control system is designed to limit the impacts that diet, exercise and other environmental factors have on the amount of fat we store. Yet faults in a person's biological system may block or hinder the normal response to these factors, making the body more susceptible to added calories and restricted activity.
Schwartz noted that changes in society over the years, including the increase in sedentary labor, have highlighted the subtle but persistent abnormalities in weight regulation.
"It's genetic factors that appear to influence a person's tendency toward weight gain," explained Schwartz. "This provides a framework to develop different types of approaches for predicting and treating obesity. "For those who are sensitive to leptin, this hormone may be an effective treatment for weight control. And for those resistant to leptin, drugs are being developed that can bypass this defect to help achieve weight loss."