Women who lose weight through exercise develop a high level of the appetite-stimulating hormone ghrelin, according to the research. Other research has found that this hormone, ghrelin, also shows at a high level in people who lose weight through dieting. Ghrelin is manufactured by the body to stimulate appetite.

It seems that the human body protects itself from weight loss by creating a desire to eat. This adaptation has been important at times of famine, but in combination with an abundance of high-calorie food it may have contributed to the current obesity epidemic."Researchers have found that weight loss triggers an adaptive response in the body to resist further weight loss," said a co-investigator of the study, Dr. Anne McTiernan.

Researchers monitored weight loss and ghrelin levels for more than 160 overweight women, randomly assigned to participate in an aerobic-exercise program or a stretching program during one year. These women didn't exercise regularly. To read the rest of this article, go to , an online weight loss community featuring calorie counter, carbs counter, BMI calculator, diet planner, workout planner and other weight loss tools.

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