Surprising study finds exercise creates “healthy” version of fat tissue. News comes just in time for holiday gorging.

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The News:

According to a timely new study, a single session of exercise may change the molecular workings of fat tissue in ways that, over time, should improve metabolic health.

This finding has particular relevance during the holidays, when, despite best intentions, many add to their fat stores. Exercise might make these annual festivities less metabolically damaging than otherwise, says The New York Times.

Rather than inert and unwelcome, fat is, in fact, a busy and necessary tissue, producing and sending out multiple biochemical signals that affect biological operations throughout the body.

Fat tissue’s most important responsibility, however, is to securely store fat, the Times points out. Hopefully, it performs this function well. Thought-provoking research in both animals and people has recently found that, if a person’s or animal’s fat tissue is relatively leaky, allowing fatty acids to seep into the bloodstream, those wandering fat beads can accumulate in other tissues, particularly the muscles and liver. Once there, they contribute to the development of insulin resistance, a serious metabolic condition that often leads to diabetes.

In a study published earlier this year, for instance, scientists from the University of Michigan and elsewhere found that if overweight men and women had low levels of fatty acids in their bloodstream, they also were metabolically healthier than other overweight adults.

Even more interesting, they also generally had healthy fat, the scientists found, with biopsies showing less inflammation and scarring than in the fat from other overweight men and women.

Presumably, the scientists speculated, this stout fat was leaking less than the feebler variety. But such study did not examine why some people had healthier fat than others and whether the state of anyone’s fat tissue might be changed.

So for the new study, which was published in the Oct. 7, 2017 issue of the Journal of Applied Physiology, the same group of scientists began to consider exercise.

Exercise, the Times notes, is known to affect the amount of fat we store, since muscles use fatty acids as fuel. Exercise also is believed to induce small amounts of white fat to convert into brown fat, a particularly desirable form of fat that burns a lot of calories.

What has not been clear is whether exercise directly alters the health of white fat tissue.

To find out, the researchers first gathered 20 men and women who were overweight but did not have insulin resistance. Eight of them exercised regularly. The others had been sedentary. The researchers tested their volunteers’ body compositions and took fat samples. Then they had each volunteer exercise on a treadmill or stationary bike for an hour at a moderately tiring pace.

An hour later, the scientists repeated the fat biopsies.

Examining the various tissues microscopically afterward, the researchers found several provocative differences. In almost all the volunteers, the fat tissue after exercise showed greater amounts of a protein that is known to contribute to the development of more blood vessels.

“More blood vessels in tissue means greater blood flow,” says Jeffrey Horowitz, a professor of movement science at the University of Michigan School of Kinesiology, with augmented delivery of oxygen and nutrients and better overall tissue health.

Interestingly, the fat tissue from those volunteers who regularly exercised also showed a small but meaningful increase in genetic activity related to blood vessel proliferation, suggesting that their tissue was more primed than that from the sedentary volunteers to start creating additional blood flow.

Their fat tissue also showed a slight increase in the gene expression of a substance that helps to reduce inflammation.

These alterations were subtle, Dr. Horowitz said. But they occurred consistently and after a single session of exercise, he points out, and might, with continued exercise, be expected to improve fat health over time.

Dr. Horowitz understands the public conundrum. “There is no doubt that the best thing for metabolic health is to lose weight.”

But at this time of year, he says, when fat gain is common, a brisk walk or jog might make this added fat healthier and more stable, and the broader effects on our bodies a little less concerning.

Steve’s Take:

Decades ago when I began running marathons, the group with whom I trained and competed embraced as dogma the belief that: “All fat is bad. Always was; always will be.”

That was then.

Now, as reported by the Times in the American Journal of Physiology Endocrinology and Metabolism, although most obese people develop insulin resistance, which can lead to type 2 diabetes and other chronic diseases, about one-third of the 30 obese adults in the study didn’t.

Steve's Take: Regular #exercise can create 'healthy #fat' mitigating some of its harmful impacts. Click To Tweet

So, what shielded them?

Adipose tissue samples revealed that the healthier group broke down fat at slower rates, and they had fewer proteins involved in fat breakdown and more involved in fat-storing. They also had fewer fibrotic cells in the adipose tissue, which allows tissue to be more flexible, and lower activation of certain inflammatory pathways.

“It sounds counterintuitive, but if we can better understand how to store fat more effectively, and why some people are better at this than others, perhaps we can design therapies and preventions that will improve some of these obesity-related metabolic conditions,” Dr. Horowitz, who led the study, says.

In the second study in the Journal of Applied Physiology, researchers found that just one session of exercise triggered signals that led to the growth of new blood vessels in fat tissue. There were also indications that regular exercisers had more blood vessels in their fat tissue than non-exercisers.

Bottom Line:

“We believe that the regular exercise we do now may create a healthier fat-storing environment for those times when we do overeat and gain weight,” Horowitz says.

The studies also support the notion that clinicians need to redefine their view of fat, Horowitz says.

Included among everything else I hadn’t been aware of, “Adipose tissue is scorned because most people see it as causing disease and obesity. But in general, adipose tissue doesn’t cause people to gain weight and become obese; it’s just where we store our extra energy when we do overeat,” Horowitz says. “Our studies aren’t suggesting it is healthy to be obese or to overeat–but when we do overeat, it is important to have a safe place to store that extra energy.”

So, gorge away my fellow merrymakers. But no matter what time of day you choose to do so, plan your subsequent “healthy fat” workout at least two to three hours after your meal.

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