June 17, 1997
How the brain knows when the body loses weight — Research provides clues about the role of the nervous system in regulating body fat
Knowledge of how the brain responds to weight loss and weight gain is advancing research toward the development of effective treatments for obesity, anorexia and other weight disorders.
In a review article appearing in the June 19 New England Journal of Medicine, Drs. Michael Schwartz and Randy Seeley of the University of Washington, Harborview Medical Center and VA Puget Sound Health Care System provide an overview of research into weight regulation and the role of neuroendocrine responses.
“By identifying the brain’s response to weight loss in the body we can begin to understand how a person’s body weight is normally controlled,” said Schwartz. “This points the way to potential treatments that may successfully help people control their body weight.”
The authors note that central to research on weight regulation is an understanding of how the hormones leptin and insulin affect the body’s metabolic functions. This includes the activation of neuropeptide Y, a brain chemical that is a potent stimulator of food intake.
“It appears that leptin and insulin can block signals in the brain that trigger normal responses to weight loss, including the increase of food intake,” said Schwartz. “Problems with weight regulation, including obesity and weight loss, can occur due to disorders in these hormonal pathways.”
The authors note that weight gain after dieting may be linked to a reduction in the levels of leptin and insulin, hormones that curb appetite and are needed to maintain stable weight. Supplementing leptin in such persons (research currently in clinical trials) may therefore attenuate responses to weight loss and help in maintaining a stable weight.
Disturbances in the control of body weight occurring within the central nervous system may also contribute to weight loss associated with illness, such as AIDS or cancer. Schwartz explains that while a person who is dieting or is forced to skip a meal normally becomes hungry, people with such illnesses do not receive the neuronal signals triggering appetite.
“These differences will remain the focus of continued research,” Schwartz notes. “If we can first understand and identify the normal responses in the brain, we should be able to find ways to fix those instances where signals go awry and result in weight loss or weight gain.”