Tuesday September 19 8:01 AM ET
Obesity hormone may curb sweet tooth

By Suzanne Rostler

NEW YORK (Reuters Health) - If you can't stomach the thought of trading in your morning sticky bun for a bowl of bran flakes in the name of good health it may be a hormone--not a character flaw--that is to blame.

According to results of a study conducted in mice, leptin--the ``obesity hormone''--appears to squelch cravings for sweet foods by targeting taste receptors on the tongue. A lack of leptin, or the body's failure to respond to the hormone due to defects in leptin receptors, may contribute to the so-called 'sweet tooth' that is the bane of countless dieters.

Leptin, a hormone produced by fat cells, is involved in weight regulation. It is thought that the hormone signals the brain when fat cells are ``full,'' but exactly how the hormone controls weight is not entirely clear.

The findings suggest that the tongue ``is a...target for leptin, and that leptin may be a sweet-sensing modulator (suppressor) that may take part in regulation of food intake,'' Dr. Kirio Kawai of Tokyo Medical and Dental University in Japan, and colleagues report.

The results of their study on mice are published in the September 26th issue of the Proceedings of the National Academy of Sciences.

According to Dr. Steven Heymsfield, deputy director of the obesity research center at St. Luke's-Roosevelt Hospital Center in New York City, the results may explain why obese animals and humans without leptin, or with defective leptin receptors, become obese.

``Variations to taste is a major component to why humans and animals eat,'' he said. ``Maybe this study begins to identify why people have different taste preferences and (become) obese because of them.''

In other words, variation in leptin, or leptin receptors, may determine why some people are more likely to eat calorie-rich sweet foods, thereby contributing to weight gain. Past studies have found that obese individuals have too much, not too little leptin, and may have lost their sensitivity to the hormone.

Heymsfield suggested that eventually, the findings might be used to develop drugs that target taste, thereby affecting food cravings and weight gain.

To investigate the effects of leptin on taste buds, Kawai and colleagues injected a group of healthy mice with leptin and gauged their reactions to sweet, salty, sour, and bitter substances. The mice were less interested in sweet tastes such as sucrose and saccharin after the injection but were no less interested in other tastes, the investigators found.

Other mice were bred to become diabetic and to have defective leptin receptors on their cells. These mice did not appear to be less interested in sweet foods even after they were injected with the hormone.

SOURCE: Proceedings of the National Academy of Sciences 2000;97:11044-