Exercise may Affect Appetite Hormones

A new study suggests that exercise may help suppress appetite, with vigorous aerobic exercise having greater effects than non-aerobic exercise.

In the study, published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, the researchers looked at two of the major appetite suppressants, ghrelin and peptide YY. Ghrelin is the only hormone known to stimulate appetite. In contrast, peptide YY suppresses appetite.

During the study, 11 male college students completed three different exercises session. During the first session, they ran for 60 minutes on a treadmill and then rested for seven hours. During the second session, they lifted weight for 90 minutes and then rested for six hours and 30 minutes. During the third session, they did not exercise at all.

During each session, the participants filled out surveys in which they rated how hungry they felt at various points. They also received two meals during each session. The researchers measured ghrelin and peptide YY levels at multiple points along the way.

The authors found that the treadmill (aerobic) session caused ghrelin levels to drop and peptide YY levels to increase, indicating the hormones were suppressing appetite. However, the weight-lifting (non-aerobic) session produced a mixed result. Ghrelin levels dropped, indicating appetite suppression, but peptide YY levels did not change significantly.

Based on the hunger ratings the participants filled out, both aerobic and resistance exercise suppressed hunger, but aerobic exercise produced a greater suppression of hunger. The changes the researchers observed were short term for both types of exercise, lasting about two hours, including the time spent exercising, reported senior author, David J. Stensel of Loughborough University in the United Kingdom.

"The finding that hunger is suppressed during and immediately after vigorous treadmill running is consistent with previous studies indicating that strenuous aerobic exercise transiently suppresses appetite," Stensel said. "The findings suggest a similar, although slightly attenuated response, for weight lifting exercise."

Previous studies have been inconclusive about whether exercise decreases ghrelin levels, but this study may help explain those mixed results, according to the researchers.

Ghrelin comes in two forms, acylated and non-acylated. The researchers measured acylated ghrelin, also called active ghrelin, because it can cross the blood-brain barrier and reach the appetite center in the brain. Stensel suggests that future research concentrate on active ghrelin.

While the study suggests that exercise suppresses appetite hormones, the next step, according to the authors, is to establish whether this change actually causes the suppression of eating.

References
1.American Physiological Society. www.the-aps.org
2.Broom DR, Batterham RL, King JA, et al. The influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin and peptide YY in healthy males. Am J Physiol Regul Integr Comp Physiol. 2008 Nov 5. View Abstract
3.Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com . Copyright © 2008.

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