You might not know it to look at most Americans, but our bodies do have a mechanism — called a "satiety hormone" — which tells us to stop eating when we're full.

A new study has found that taking of a synthetic form of this hormone, pramlintide, may help us avoid binge eating and reduce our appetite for high-fat and sweet foods.

Pramlintide is a synthetic form of amylin, a satiety hormone produced naturally by the pancreas.

"Satiety hormones are commonly thought to control food intake by signaling to the brain when we are full," said Christian Weyer, M.D., the study's senior author and executive director of clinical research at Amylin Pharmaceuticals, Inc., in San Diego, Calif. "The findings of our clinical study further suggest that satiety hormones such as amylin can exert multiple effects on human eating behavior, such as reduced intake of highly-palatable foods and reduced binge eating tendency."

These findings are based on a 44-day study of 88 obese people who were given pramlintide and a placebo.

Subjects continued their typical exercise routines and made no other changes that could account for weight loss. Food intake was monitored. Subjects were told to eat until they felt full.

On days 1, 3 and 43, subjects were offered foods such as bagels and cream cheese, muffins, cereal, fruit, sandwiches, casseroles, salads, tortilla chips, potato chips, cookies and soft drinks. They were also offered an evening snack that included peanut butter sandwiches and a cookie.

On inpatient days 2, 4 and 44, they were given a high-fat, high-sugar lunch that included deep-dish pizzas, ice cream and high fructose corn syrup-sweetened soft drinks. These meals were the nicknamed the "fast-food challenge."

Subjects rated their feelings of hunger, fullness and nausea throughout the study, using an electronic device. They also completed a questionnaire designed to measure binge eating tendencies. Researchers then analyzed weight, portion size, 24-hour caloric intake and consumption at the "fast food" challenge.

The results:

Those who received pramlintide lost significantly more weight than those in the placebo group. The pramlintide group lost an average of 4.5 pounds, about 2% of total body weight, while the placebo group remained about the same weight.

The pramlintide group ate fewer calories and felt just as full and satiated as the placebo group, even though the pramlintide group was eating considerably less. The pramlintide group also ate less fast food — by 385 calories — than the placebo group.

Those taking pramlintide also scored better on a questionnaire designed to measure binge eating tendencies.

"Our findings illustrate that comprehensive, carefully conducted clinical studies can provide important new insights into how hormones help regulate human eating behavior," Weyer said.

The study appears in the June 2007 online edition of the American Journal of Physiology-Endocrinology and Metabolism.