Exercise helps stoke fat-burning fires
It may be easier for active people to stay slim after a few days of eating too much fat, a new study shows.
Given that eating lots of fat over short stretches likely leads to accumulation of excess body fat over time, Dr. Kent C. Hansen of the University of Wisconsin in Madison and his colleagues write, regular exercise may help people maintain a healthy weight even if they do indulge occasionally.
While the body can adjust fairly rapidly to excess carbohydrate intake by boosting the rate at which it burns calories from carbs, it takes several days to adjust in a similar way to an increase in fat intake, Hansen and his team note in the January issue of the American Journal of Clinical Nutrition. However, there is evidence that exercise can help the body adapt more quickly, they add.
To investigate, the researchers had a group of 10 sedentary women exercise at three different levels as they switched from a low-fat diet with 30% of calories from fat to a four-day, high-fat diet in which fat provided 50% of their energy. The exercise levels included remaining sedentary; burning 150 calories on an exercise bike, which took about an hour; or burning 300 calories, which took about two hours.
The more a woman exercised, the faster she was able to burn fat calories once she had switched to the high fat diet, the researchers found.
The current study can’t explain why exercise helped the women burn fat, the researchers note, but it may have helped shift the fat they consumed toward active tissues such as skeletal muscle, as well as boosting activity of fat-burning enzymes in those tissues.
“Because short-term consumption of high-fat diets is thought to contribute to excess fat accumulation, regular exercise should be protective and should help maintain a healthy body composition,” Hansen and his team conclude.
SOURCE: American Journal of Clinical Nutrition, January 2007.
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