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More Evidence of the Anti-Aging Power of Exercise

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Telomeres and the Special Role of Strength Training

We are learning more and more about the effects of exercise on aging at the cellular and molecular level. Not long ago I wrote about a study showing that six months of progressive resistance training made the gene expression pattern of aging mitochondria appear significantly younger (article 192 in our Age Factor category). Now we have two more studies. One shows how exercise protects DNA from the wear and tear of aging. The other demonstrates how fast-twitch muscle fibers precipitate fat loss and improve metabolic function.

In the first study, scientists at King’s College in London and colleagues measured telomeres in twins to gauge the effect of exercise on aging. (January 28, 2008, Archives of Interval Medicine)

Telomeres cap DNA chromosomes in cells and protect them from damage. Unfortunately, they progressively wear and shorten from repeated cell division, oxidative stress, inflammation, and other detrimental processes, eventually leaving the chromosomes unprotected. When the caps are eroded or gone, the wear begins to cut into genes which are important to bodily functions. Scientists believe that as telomeres shorten and more cells are damaged and discarded over time we age.

In the words of the researchers, “telomere dynamics…might chronicle the cumulative burden of oxidative stress and inflammation and, as such, serve as an index of biological age.”

The purpose of the study was to test the hypothesis that “physical activity level may have an [independent] effect on telomere attrition,” lead author Lynn Cherakas, PhD, and her colleagues wrote. In other words, does exercise delay aging as shown by this marker? 

To find out, they studied 2401 twins (2152 women and 249 men, aged 18 to 81), who were part of a UK Adult Twins Registry, using questionnaires on physical activity level (leisure and at work), smoking status, disease status, and socioeconomic status. Height and weight was recorded during clinical visits. In addition, DNA was extracted from blood samples, and telomere length was measured.

Here’s what the researchers found.

Telomere length does in fact decrease with age. Women and men who are physically active, however, have longer telomeres than those who are sedentary. This is true even after adjusting for the influence of age, weight, disease, socioeconomic status, and smoking.

Subjects who spent more than 3 hours each week in vigorous physical activity (such as running, cycling, and lifting weights) had longer telomeres than subjects 10 years younger, who exercised less than 16 minutes a week. “This difference suggests that inactive subjects may be biologically older by 10 years,” the researchers wrote.

Interestingly, this finding held true for exercise during leisure time, but not exercise at work. Physical activity at work does not appear to be as protective, perhaps because it is required and involves more psychological stress.

Significantly, a unique group of 67 pairs, where one twin exercised significantly more than the other, confirmed the overall finding that exercisers have longer, seemingly more durable telomeres. This finding strongly suggests that the difference was due to lifestyle factors alone. Twins, of course, are ideal subjects for isolating the role of lifestyle, because fraternal twins share the same parents (and 50% of the genes) and identical twins share the same genes.

The researchers suggest that exercise may inoculate the body against oxidative stress and “up-regulate anti-inflammatory processes,” but exactly how this works has yet to be explained; it remains an enticing mystery. While more study will be required, this finding is clearly good news for those of us who enjoy being active.

“Our results underscore the vital importance of [regular physical activity],” say Dr. Cherakas and her colleagues. 

(My friend Richard Winett, PhD, reported on this study in the April, 2008, issue of Master Trainer newsletter.)

The next study deals with obese mice, but has important implications for the role of strength training in delaying the aging process.

Fast Fibers Reduce Fat and Speed Metabolism

In a widely reported Boston University Medical School study, published in the February 6, 2008, issue of Cell Metabolism, researchers found that replacing slow and enduring (type 1) muscle fibers with stronger and faster (but less enduring) type 2 fibers produced a reduction of fat mass and insulin resistance. (Endurance training normally develops type 1 fibers, and strength training builds type 2.)

This was accomplished using a genetically engineered mouse (MyoMouse), with a muscle-growth regulating gene called Akt1. The special gene could be turned on and off at will by the researchers. Activating Akt1 caused the mice to grow type 2 fibers, without exercise. (Needless to say, mice don’t pump iron on cue.) When the gene was de-activated, the mice again develop a predominance of type 1 fibers.

That’s a pretty neat trick and probably not feasible in humans, but the implications are huge. With the gene on, the mice take on the characteristics of a lean and powerful sprinter or a weight lifter. Turned off, the mice revert to their original state.

The MyoMouse is obese and insulin resistant when the gene is deactivated. It is fed a high-calorie diet with lots of fat and sugar, like you might get at a fast food restaurant. The kicker is that the transformation took place with no change in diet. The mice with the activated gene continued to eat the same fattening diet.

“Remarkably, type 2 muscle growth was associated with an overall reduction in body mass, due to a large decrease in fat mass. In addition, blood tests showed that these mice became metabolically normal [with no insulin resistance],” said senior author Kenneth Walsh, PhD, a professor of Medicine at Boston University. “This work shows that type 2 muscle just doesn’t allow you to pick up heavy objects, it is also important in controlling whole body metabolism,” he said.

“It appears that the increase in type 2 muscle fiber orchestrates changes in the body through its ability to communicate with other tissues,” Walsh continued.

Importantly, this is a previously unappreciated benefit of powerful, type 2 muscle fibers. It suggests that strength training may be especially beneficial to overweight and insulin resistant individuals.

This finding also helps to explain why most people get fatter as they age.

Fat gain has come to be thought of as a normal part of aging.  

“Beyond the age of 30, humans lose approximately 6 pounds of muscle mass per decade. Thus a 50-year-old may be relatively good at playing tennis or jogging because type 1 muscle is preserved, but a measurement of grip strength or core body strength could show appreciable declines,” Dr. Walsh explained. That, of course, would indicate a loss of type 2 muscle, and probably fat gain as well.

The new study suggests what can be done about it.

In a commentary published in Cell Metabolism along with the study, Brooke and Leslie Leinwand of the University of Colorado at Boulder wrote: “These findings indicate that interventions designed to increase skeletal muscle mass…may prove to be critical weapons in the fight against obesity and obesity-related [ailments], including diabetes, heart disease, stroke, hypertension, and cancer.”

The key point here is that weight training appears to be as effective as aerobics for fat loss and weight control—and perhaps more effective. The rap against barbell training has always been that it doesn’t burn many calories. The MyoMouse study, where fat mass was lost all over the body without an increase in physical activity, suggests that calorie-burning exercise isn’t necessary—it helps, of course, but is not essential. Endurance training burns lots of calories, but strength training appears to do something even more important: It turns the metabolism into a fat-burning machine.

Strength training advocates have been saying this for a long time—and this study provides strong evidence that it’s true. Weight trained muscle keeps the metabolic furnace burning bright. 

Here’s the hopeful message: Lift weights throughout life, and you will not only maintain muscle mass, you will gain less fat and be healthier as you age. Combine strength training with aerobic exercise and you almost cannot miss. (Hmmm, seems that I’ve heard that before.)

If you are not a super mouse, it would also be a good idea to go easy on concentrated-calorie foods and refined carbohydrates.

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