Exercise helps dieters slim down in more ways than one, researchers say

Dieters everywhere know that exercise is a key component of any weight-loss regimen. To drop pounds, you have to burn more calories than you take in.

But exercise helps in another way too – it resets the chemicals in your brain that regulate appetite.

That’s the conclusion of a study published Tuesday in the journal PLoS Biology.

Brazilian researchers discovered this by forcing obese rats to swim or spend some quality time on a treadmill. Then they monitored their food intake over the next 12 hours. Sure enough, the post-workout rats ate less than their sedentary counterparts. In fact, they ate the same amount as lean rats.

Additional experiments verified that exercise altered the brain chemistry of the obese rats. Some key signaling molecules – which help neurons “talk” to each other balancing calories in and calories out – were restored to the levels found in lean rats. Exercise also reestablished the ability of a hormone called leptin to let the brain know when it was time to stop eating.

The initial experiments involved only two days of exercise. When the rats were made to exercise for four weeks, the researchers found that the obese rats ate less and lost weight during the first three days. After that, their appetities returned to their pre-exercise levels. However, their metabolism continued to benefit.

Exercise didn’t change the appetite or brain chemistry of lean rats, the researchers found. That makes sense because their brains were already doing a good job of maintaining a healthy weight, they said.

-- Karen Kaplan / Los Angeles Times