TWO CENTRAL truths about an aging body — the ease of acquiring a spare tire and the difficulty of losing it — were referred to by one doctor with irritating cheer as “a headwind.”
This frustrating phenomenon, and how to turn it around, preoccupies baby boomers and their elders alike. Increasingly, research suggests combining aerobic exercise with strength training not only promotes fitness, but helps reverse time’s drag on the metabolism.
Creeping obesity — Americans on average gain 25 pounds from age 25 to 65 — happens with astonishing ease, says Wendy Kohrt of Washington University. It takes only a few excess calories a day to add such weight over time. When activity wanes, it’s easy to consume more energy than we use.
But there’s much more to the story than that. With the passage of time, our metabolic rate — or the speed at which we burn calories for energy — slows down. The greater the lean muscle mass a person has the higher the metabolism. The gradual replacement of muscle with fat during aging decelerates our body’s energy-burning rate, notes Irving Rosenberg of Tufts University.
It’s a vicious cycle, but there’s hope for reversing the headwind as late as in our eighth decade of life. Of course, older people with health conditions must plan any exercise program with their doctor.
Working with volunteers in their 60s and 70s, Samuel Klein at Washington University in St. Louis, Mo., found older people have a reduced capacity to oxidize fat during exercise. Instead, most of the energy they burn consists of carbohydrates.
WHEN THE SENIORS exercised only sporadically, their fat stores were broken down but weren’t burned up by the muscles as energy; instead the fat got recycled through the liver and redeposited in fat depots throughout the body. Unfair, but true.
Whether due to aging itself, or decreased physical activity, the muscles of sedentary elderly contain fewer energy factories known as mitochondria, with fewer enzymes to break down fats to use as energy. But Dr. Klein found structured exercise training boosts both to restore a youthful fat-burning power.
“The good news is that if older people train, they can normalize their ability to oxidize fat,” he says. The 16-week program — 45 minutes of cycling, four or five times weekly — boosted seniors’ metabolisms.
Another signpost of aging is weight gain in the middle. More than an esthetic problem, “apple-shaped” bodies carry an increased risk of diabetes, high blood pressure and heart disease. But here too, exercise training can pare the problem.
Dr. Kohrt put men and women, ages 60 to 70, through an endurance exercise-training program consisting of walking and jogging on an indoor track or treadmill, plus some cycling and rowing.
Defying the conventional wisdom about the difficulty of spot-reducing, her volunteers trimmed their abdominal fat and with it, she hopes, their risk of diseases linked to “central obesity.”
There is also a nutritional strategy — supported by scientific data — that could help. These experts generally stress a common-sense regimen that includes fruits, vegetables, grains and lean protein. Such a diet, says Edward Mascioli of Harvard Medical School, can help burn calories through a process called “diet-induced thermogenesis,” that is, producing heat from calories. Fitter people eating carbohydrate-based diets burn more calories this way than do sedentary people eating fat-rich diets.
In thermogenesis, your body burns off 10 of every 100 calories consumed from carbohydrates, but only one or two calories of 100 calories from fat, he says. Better still, if you exercise within a couple hours of a meal, you’ll use up more.
A business lunch of veal in cream sauce with mousseline potatoes and wines, for example, is not very thermogenic, says Angelo Tremblay of Laval University in Ste.-Foy, Quebec. Fat-and alcohol-laced cuisine make for a sluggish metabolism.
EXERCISE-AVERSE gourmands shouldn’t throw in the towel. Paul Williams of Lawrence Berkeley Laboratory in Berkeley, Calif., says, “We ought to increase exercise as we age. Exercise is very much an investment. You get out what you put into it.” His studies are finding even trained athletes gain pounds as they age. So think of exercise as dividend-bearing shares, and redouble your investment.
Dwindling muscle, called “sarcopenia” isn’t just a cosmetic issue, but a serious medical problem in the frail elderly. “The most effective thing people can do is become physically active,” says Tufts University physiologist Ronenn Roubenoff. While cardiovascular health and fat-burning requires aerobics, he says muscle-building requires strength training. So the ideal fitness program would alternate aerobics such as brisk walking, running or cycling, with strength training using hand weights or gym equipment.
While men traditionally gravitate to weight training, and young women have joined them in droves, getting more mature women to pump iron has been a tougher sell. Miriam Nelson of Tufts University is trying to change that mindset in her book “Strong Women Stay Young,” a primer on strength training.
“Older people, especially women, are intimidated by strength training. We’re told we need walking. And yes, that’s good,” she grants. “But it seems strength training is a much more potent factor in maintaining that precious muscle.”