Put some muscle behind your diet
By TOM VALEO
Published April 17, 2007
If you want to gain weight, especially as you get older, go on a diet.
Your body will respond to the shortage of calories by burning fat, of course, but it will burn an almost equal amount of protein from your muscle fibers. If you lose 20 pounds by cutting calories, for example, about 8 of those pounds will come from muscle. If you regain the weight and diet again, you will lose more muscle.
The loss of muscle mass is already one of the biggest problems of aging. It starts around age 30. By age 50, you've lost about 10 percent of your muscle mass.
"After that it speeds up about 2 percent per year," said Chhanda Dutta, a scientist with the National Institute of Aging who studies the effect of exercise on older people. "By 80, you could have a 40 percent loss of muscle mass."
That's one reason it becomes increasingly difficult to avoid weight gain as you get older. Muscle fibers burn calories, so when you lose muscle mass, you burn fewer calories. When you diet, you lose muscle mass at a faster rate, which leaves you even more vulnerable to weight gain.
There's more bad news.
Our metabolism has been shaped over millions of years of evolution to resist weight loss. Those of our ancestors who possessed a body that held on to calories in times of food shortages were more likely to survive and procreate.
At the same time, the human body developed almost no resistance to gaining weight. Our bodies will store almost unlimited amounts of fat. And when we gain fat, we tend to become less sensitive to the hormone that makes us feel satisfied.
In other words, the heavier we get, the more likely we are to overeat.
The only bright spot in all of this is the fact that if we lift weights while dieting, we can minimize the loss of muscle mass.
"If you do resistance training during weight loss, you can pretty much eliminate loss of muscle," said Gary R. Hunter, a professor at the University of Alabama-Birmingham. "You certainly can maintain the muscle mass you have."
Lifting weights forces the muscles to work against gravity, which brings a host of benefits. Stronger leg muscles, for example, stabilize the knee, which helps reduce the pain of arthritis. Stronger leg and hip muscles also help prevent falls.
Resistance training involves lifting enough weight to fatigue the muscles after 8 to 12 repetitions. As the muscles get stronger, increase the weight. This gradual increase allows people of any age to benefit from weight lifting.
"The evidence shows that no matter how old you are, you can increase muscle mass," said Ben F. Hurley, a professor of exercise physiology at the University of Maryland.
"It doesn't take much of an increase in exercise to produce improvement, because your resting metabolic rate is with you 24 hours a day. A small increase over a year makes a huge difference. Even if you maintain the same food intake, you won't be as likely to gain weight."
Tom Valeo writes about medical and health issues. Write to him in care of Pulse, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731, or e-mail features@sptimes.com.