Regular exercise alters the way body fat behaves, converting the unhealthy white fat that forms from sedentary lifestyle to healthy brown fat that aids metabolic activity in tissues, researchers have claimed.

According to the findings of a new study conducted on mice and humans, exercise aids conversion of ‘bad fat’ into ‘good’ calorie-burning version, thus keeping diabetes at bay.

The study
For the first part of the study, Laurie Goodyear from the Joslin Diabetes Center and colleagues made mice either run on an exercise wheel for 11 days or remain inactive. At the end of the 11 day exercise period, Goodyear found that active mice exhibited a significant shift in gene expression in subcutaneous fat as compared to inactive and sedentary mice.

Researchers noted histologic changes in the subcutaneous white adipose tissue (SCWAT) known as ‘browning.’ The cells shrank, shedding some of the lipids inside and increased the mitochondria within the cell.

To determine if the brown fat affected the way in which the body used glucose, researchers transplanted the trained ‘brown’ mouse fat into high-fat, sedentary and inactive mice and found that those mice showed improved glucose tolerance and insulin sensitivity for at least 12 weeks post transplantation.

To check if the similar effects could be seen in humans too, Goodyear recruited 10 healthy men, all of whom were required to undergo 12 weeks of training on an exercise bicycle.

At the end of the 12 week exercise routine, researchers found similar ‘browning’ of fat in humans too.

“Our results showed that exercise doesn’t just have beneficial effects on muscle, it also affects fat,” said Kristin Stanford, a postdoctoral fellow at Joslin Diabetes Center in Boston. “It’s clear that when fat gets trained, it becomes browner and more metabolically active. We think there are factors being released into the bloodstream from the healthier fat that are working on other tissues.”

“We know that exercise is good for us,” added Goodyear, study’s lead researcher, “But what we’re showing here is that fat changes dramatically in response to exercise training and is having good metabolic effects. This is not the fat that’s around your middle, which is bad fat and can lead to diabetes and other insulin resistant conditions. It’s the fat that’s under the skin, the subcutaneous fat that adapts in a way that appears to be having important metabolic effects.”

The findings of the study were presented yesterday at the American Diabetes Association’s 73rd Scientific Sessions.

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