Overweight women who engaged in exercise for one to two hours a week lost several pounds over six months without dieting. But paradoxically, those who exercised even more - three hours a week - failed to lose as much as expected.
The researchers, who published their findings in PLoSONE, a Public Library of Science online journal, speculated that the reason for this phenomenon was that the women who exercised the most rewarded themselves with food treats for their “sacrifice.”
“There is a great lesson here: People generally overestimate the calories they are burning with exercise, and they may reward themselves by eating more,” said lead researcher Tim Church, director of preventive-medicine research at the Pennington Biomedical Research Center in Baton Rouge, La.
Church and his team studied 411 overweight or obese inactive women, with an average age of 57, over a period of six months. They were divided into four groups. One, the control group, was told to keep their level of physical activity the same. The other three were instructed to work out at different intensities each week, switching off walking fast on a treadmill at a fitness center and riding a stationary bike. All groups were told not to change their eating habits.
One exercise group worked out for an average of 72 minutes a week (about 10 minutes a day). A second exercised 136 minutes a week (almost 20 minutes a day). And the third sweated for 194 minutes a week (32 minutes a day).
After six months, it was found that women who exercised 72 minutes a week lost two to three pounds. The second exercise group (136 minutes a week) lost a bit more than four pounds. But the third group (194 minutes a week of exercise) lost only about two to three pounds, whereas it was expected they should have lost about six pounds.
All of those who exercised, however, lost abdominal fat, which is considered a dangerous risk factor for heart disease, diabetes, stroke and some types of cancer, Church said. In the study, even those who didn’t lose weight lost about an inch around the waist, while those who did lose weight lost on average two inches around the belly.
Regular exercise, Church said, not only reduces the risk of a host of grave medical conditions but also strengthens one’s quality of life by reducing stress, depression and anxiety, and by improving bone and joint health, sex drive, sleep and memory.
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