Wednesday, June 18, 2008

Exercise Reduces Hunger In Lean Women But Not Obese Women

“Exercise does not suppress appetite in obese women, as it does in lean women, according to a new study. The results were presented at The Endocrine Society's 90th Annual Meeting in San Francisco. ‘This [lack of appetite suppression] may promote greater food intake after exercise in obese women,’ said Katarina Borer, PhD, a University of Michigan researcher and lead author of the study. ‘This information will help therapists and physicians understand the limitations of exercise in appetite control for weight loss in obese people.’ Borer and her co-workers sought to better understand how changes in body fat level influence appetite and a hormone called leptin, which in animals curbs appetite when body fat increases. When leptin levels rise, it supposedly shuts off appetite and motivates physical activity to burn calories. However, as obese people become fatter, their leptin levels rise, but they become resistant to the actions of this hormone. ‘The hormone doesn't do the job it's supposed to do in lean people,’ Borer said. As expected, obese women had much higher leptin levels than in lean women, study data showed. But during intense exercise, obese women did not have reduced production of leptin, as lean women did. Only moderate-intensity exercise lowered leptin in obese women. ‘Obesity interferes with leptin's detection of exercise energy expenditure and with appetite suppression,’ Borer said. ‘Obese women perhaps need to consciously watch their calories because some of the hormonal satiety [fullness] signals don't seem to work as well.’”

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