Study Reveals Naturally-Occuring Hormone Can Partially Reduces Food Intake, Body Weight

Previous studies at ONPRC and OHSU helped demonstrate that PYY can inhibit food intake. Some believe PYY may be one of the body's natural signals to the brain telling people they are full and should stop eating.

"While PYY, caused some weight loss in this study, the hormone does not seem to be a silver bullet to fight obesity," said Michael Cowley, Ph.D., an assistant scientist in the Division of Neuroscience at ONPRC. "The decreases in appetite only occurred during meals early in the day. However, PYY did not affect food intake in the evening. In addition, high doses of PYY are required to cause weight loss. While we're pleased with the progress of this research, we have a long way to go before there's a weight loss drug available to consumers."

"These were short-term studies and caused mild weight loss. This is a long way from knowing if chronic treatment will cause stable weight loss," said study co-author and ONPRC scientist Kevin Grove, Ph.D. "While the studies showed that PYY caused mild but reliable inhibitions in food intake, we still want to know if the drug promotes weight loss through changes in metabolism. If PYY does increase metabolism, it may be useful in combination with other therapies, or with diet and exercise, to prevent weight regain."

To conduct the research, scientists studied nine rhesus macaque monkeys fed high-fat diets and given infusions of PYY at differing intervals throughout a two-week period. During that time, scientists measured PYY levels in the body and tracked weight changes in the animals. Analysis of the data revealed that animals given high doses of PYY twice daily averaged 2 percent body weight loss that was maintained during two weeks of treatment.

"There is an urgent need for improved therapies for weight loss assistance in the United States," explained study co-author and ONPRC scientist Judy Cameron, Ph.D. "The country is currently facing an obesity epidemic. This health crisis can also be linked a variety of associated disorders, including skyrocketing diabetes rates and heightened heart and stroke risks. Clearly, by attacking the obesity issue, we may be able to prevent many other life-ending illnesses."

The research was supported by the National Institutes of Health and the Fogarty International Center.

The ONPRC is a registered research institution, inspected regularly by the United States Department of Agriculture. It operates in compliance with the Animal Welfare Act and has an assurance of regulatory compliance on file with the National Institutes of Health. The ONPRC also participates in the voluntary accreditation program overseen by the Association for Assessment and Accreditation of Laboratory Animal Care International.