Can weight training prevent diabetes?

With the booming popularity of weight lifting DVDs like P90X, many men — the target audience of these videos — have made strength training their only form of exercise. As it turns out, working to bulk up those muscles not only helps build strength and prevent age-related muscle loss, but may help ward off type 2 diabetes as well.

In fact, it may work nearly as well as steady aerobic exercise such as walking, swimming, and biking. That’s what Harvard School of Public Health researchers found when they followed more than 32,000 men for nearly two decades: Those who reported doing 30 minutes a day of resistance training at the beginning of the study had a 34 percent decrease in their diabetes risk compared with those who didn’t exercise. Men who did 30 minutes a day of aerobic activity had a 52 percent lower risk of diabetes compared with couch potatoes, according to the study published last Monday in the Archives of Internal Medicine.

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The best form of exercise for diabetes prevention? Combining steady exercise and weight training at least 30 minutes a day most days of the week. Study participants who did both had nearly a 60 percent reduction in diabetes risk. (Among all the men, about 7 percent developed diabetes during the study.)

“Our study was the first to look at whether weight training provided benefits long-term in lowering the incidence of diabetes,’’ said study coauthor Dr. Frank Hu, a professor of nutrition and epidemiology. “While the study didn’t include women, there’s no reason to believe that the finding doesn’t apply to them as well.’’

Another finding published in the same journal analyzed data from five studies and found that diabetics who reported moderate levels of physical activity — whether hauling lumber on the job or walking regularly with friends — had a 38 percent lower risk of dying of any cause compared with diabetics who didn’t engage in any exercise.

Strength-training activities trigger muscle cells to utilize more glucose for energy, which can lower blood sugar levels, said Hu. An increase in lean body mass also helps make cells more sensitive to the hormone insulin, helping to reverse insulin resistance, a precursor of diabetes. Aerobic activity, he added, probably works through different mechanisms to help prevent diabetes by encouraging fat loss and insulin sensitivity through calorie burning. Thus, combining the two may be ideal for both preventing and managing diabetes.

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“I cannot help but note that none of the time I spend trying to decide whether to increase the dose or add a new medication for my patients with type 2 diabetes is likely to result in a 38 percent reduction in mortality,’’ wrote Dr. Mitchell Katz, in an editorial that accompanied the study. He urged doctors to write specific exercise prescriptions for patients with diabetes and those at risk — such as 30 minutes of brisk walking three times a week and two days a week of muscle-building activities.

Joslin Diabetes Center provides an exercise program in its on-site gym that includes a strength-training component, often using resistance bands, for diabetic patients who might be reluctant to purchase free weights or join a gym. The specific benefits conferred by strength training are “really newly recognized,’’ said Jacqueline Shahar, a clinical exercise physiologist at Joslin. “Ten years ago, the exercise program we provided was strictly aerobic, but now everyone gets a program that includes resistance training.’’

While insurance providers in the state cover the cost of the Joslin exercise program — which runs upward of $100 per session — for those diagnosed with diabetes, they often don’t cover the program in those who are at risk of becoming diabetic because of insulin resistance or strong family history.

The new Harvard study could provide an impetus for managed care companies to pick up the exercise tab for those who don’t yet have diabetes, to prevent the condition and the long-term complications that go along with it, including heart disease, blindness, and nerve damage. But that may not happen until better-designed studies can demonstrate that exercise itself can prevent diabetes. Deborah Kotz

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ZoningLit wrote: It’s nice to see the medical community and the health media catching on to what elite athletes have known for a decade or more.

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