A new study shows the benefits of exercise-stoked cellular clean-up.
It's hardly breaking news that exercise does wonders for mind and body betterment — it burns calories, reshapes your body, wards off diseases, slows aging, puts you in a good mood and, well, the list goes on. But as of last month, we may better understand some of the reasons why getting a move on is such a powerful health tool: It takes out your body’s trash.
According to recent research published in the journal Nature, scientists at the University of Texas Southwestern Medical Center found that exercise may stimulate autophagy, or "self-eating," a process in which the body’s cells literally clean themselves up so that they can continue to function properly. Study co-author Beth Levine, a pioneer in autophagy research, calls it "an intracellular recycling system" that works by surrounding the cellular trash with a membrane, breaks it down, then burns it for energy. Getting rid of this cellular trash, which may be caused by bacteria, injury or the normal aging process, keeps cells functioning properly and may help suppress tumors and inflammation, slow aging and strengthen your immunity against viruses and infectious diseases.
The study compared the muscle cells of two groups of mice — one with normal trash pick-ups (i.e., normal-functioning levels of autophagy) and the other bred with messy muscle cells designed not to activate autophagy during exercise. The researchers fed both the control group and the mutants a high-fat diet that gave them diabetes. Then they sent them running.
The results were clear: The mice which could not activate autophagy through exercise got tired much more quickly than the normal trash-removing mice. They also couldn’t burn up the sugar in their bloodstream, so they maintained their diabetes and had higher levels of cholesterol, whereas the mice with the normal autophagy function reversed their disease.
Bottom line: When the exercise-autophagy link was switched off, exercise did not make the mutant mice healthier and fitter. Does this mean that autophagy is the key reason why exercise makes you fitter … and makes you live longer … and stops chronic diseases … and all the rest? Maybe.
"Autophagy is very hot now, and this is a very exciting, interesting piece of research done by a very reputable group," says Paul Spector, MD, ASCM, a Columbia-trained physician and Tier 4 trainer at Equinox in New York City with a focus on the effect of diet and exercise on aging and disease. "But it is very early in the story — after all, it’s mouse tissue, not human."
Still, Spector admits that the new research may help position autophagy — and therefore exercise — as a key tool in disease prevention and anti-aging. "Knowledge of autophagy has been around for a long time, and we thought until recently that it was the body’s way of removing cells gone bad," he says, "But studies like this show that autophagy has a lot of functions — including prevention of cells going bad."
"We are in a chronic state of sympathetic nervous system arousal — the fight or flight mechanism — and it is not followed by motor activity unless you exercise,” says Spector. In other words, without exercise, there’s no clean-up crew to mop up the stress, which is manifested in the form of high blood pressure, high cortisol levels and diminishing insulin sensitivity.
The same crew, it seems, is also responsible for keeping you young. "The 'Disposable Soma' theory, a Darwinian model which postulates that we stay healthy only until we reproduce, then begin to fall apart, could be due to a failure of DNA maintenance — a failure of cellular housekeeping," says Spector. "In a person over 50, when you see skin becoming wrinkled and eyesight going bad, it may very well be the result of biological trash accumulating all over the body."
Spector says the human body is, in many ways, no different than any machine that must be maintained. Not keeping the gears and circuitry clean gums up the mechanisms — and even gums up the cleaner. "It’s a vicious cycle: autophagy can only take care of so much, and gets impeded and overwhelmed by too much toxic trash."
While it remains to be seen whether running humans respond like a bunch of running mice, the findings point to physical activity as a key force in keeping your cells, and their cleaning mechanism, in tip top shape. "The best way to fight all the symptoms of aging is to be in prevention mode,” says Spector. And that, of course, means exercise.