Leptin and Insulin: The Effects of Glucose and Fructose

An upcoming study should help reveal how two kinds of sugars in our foods, glucose and fructose, affect the body’s production of leptin and insulin.

Agricultural Research Service chemist Nancy L. Keim, Peter J. Havel and Craig H. Warden, a genetics and pediatrics researcher at U.C. Davis, are collaborating in this leptin and insulin investigation.

“When we eat or drink foods with glucose in them,” explains Havel, “the glucose triggers release of leptin and insulin. Both of those hormones help regulate our appetite. However, when we eat or drink foods with fructose in them, like soft drinks or some juice beverages, our bodies may produce less leptin or insulin. As a result, we may still feel hungry after eating. It’s as if the fructose-containing foods are invisible to our bodies, so our appetites aren’t adjusted after eating them.”

In the new study, Havel hopes to determine whether fructose is indeed “unrecognized by our central nervous system.”

Keim wants to find out if leptin helps boost metabolism, the rate at which we burn calories. That happened in tests done elsewhere on laboratory animals.

Animals deficient in leptin burned more calories when they were given additional leptin.

Also, a study of leptin levels in young children showed that those with higher leptin levels apparently burned more calories when they were active.

Marcia Wood, Agricultural Research Service Information Staff, Agricultural Research Service.

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