Belly Fat Booms When Activity Stops

March 18, 2008 -- Belly fat doesn't waste any time in gathering, given the chance. And a few weeks of inactivity may be all the chance it takes.

So say researchers including Rasmus Olsen, MD, of Denmark's Centre of Inflammation and Metabolism. They studied 10 healthy young men who were active, but not avid exercisers.

When the study started, the men walked 6,000 to 10,000 steps daily. But they didn't work out for more than two hours per week.

For the study, the men backed their activity way down, logging only 1,500 steps per day for two weeks. They got body scans to track their overall fat and their belly fat before and after their sedentary spell.

Overall, the men didn't gain any obvious fat. But their belly fat, located deep inside the abdomen, rose by 7% during the study.

Belly fat has been linked to increased risk of heart disease and diabetes. And previous research has shown that exercise cuts belly fat, which is also called visceral fat.

Belly fat isn't the only risky trend that started soon after activity stopped.

After three weeks of reduced activity, eight healthy young men became less sensitive to insulin, a hormone that controls blood sugar.

And those men's ability to handle fatty food also faltered.

The men ate a fatty meal before and after three weeks of reduced activity. They provided blood samples right after that meal so that their triglycerides, a type of blood fat, could be measured.

Triglyceride levels soared higher after the fatty meal when the men were idle, compared to in their active heyday.

The findings appear in a letter published in The Journal of the American Medical Association's March 19 edition.

As far as those findings show, the men were still healthy after their bout of inactivity. And it's not clear if their eating habits changed while they were inactive. But their history of activity wasn't a hedge against the risks of being sedentary.

The bottom line: If you become inactive, the body won't let you coast for very long, though those shifts may not be noticeable at first.