July 21, 2005
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Joe Fornabaio for The New York Times
A strict regimen of light weights will build endurance but not muscle.
July 21, 2005
Weight-Loss Theory Is Losing Some of Its Strength
By MARTICA HEANER
BARBARA WOODWORTH, 35, a social worker in Seattle, wanted to drop 40 pounds. Alisa Rivera, 39, a college adviser at the University of California, Los Angeles, also wanted to lose weight. She also wanted to build long, lean muscle. So the two women routinely began to lift weights. But like many of the other 36 million women nationwide who each year pick up dumbbells hoping to lose pounds or develop a sculptured body, both Ms. Woodworth and Ms. Rivera ended up disappointed because the strategy is not as simple – or as effective – as it sounds.
Personal trainers, fitness instructors, magazines and books have sold a double-barreled promise that any strength training builds muscle and that having more muscle dramatically speeds metabolism, increasing the calories a person burns while at rest. With all that extra calorie burning, the story goes, excess weight comes off effortlessly.
The story is wrong in two ways, researchers say. First, muscle is not such an amazing calorie burner. “Even if weight training increases muscle and metabolism, there is little evidence showing that it is enough to cause weight loss,” said Joseph Donnelly, the director of the Energy Balance Laboratory at the University of Kansas, who has extensively reviewed studies on the link between resistance training and weight loss.
And second, many who try weight training – especially women – fail to do what it actually takes to build more muscle. They lift too light a weight, or they neglect to progress to heavier weights as they grow stronger. And often, women who take up weight lifting also diet. In fact, it is nearly impossible to increase muscle while cutting calories.
Regular resistance training, done correctly, has many benefits. It can prevent some of the muscle loss that occurs with weight loss. It can also lower body fat levels and even help preserve bone mass. But the idea that it can magically increase calorie-burning is “a very big stretch,” said Edward Melanson, an assistant professor in the division of endocrinology, diabetes and metabolism at the University of Colorado Health Sciences Center in Denver. Claims that resistance training can send metabolism skyrocketing are easy to find. A Google search using the terms “metabolism” and “weights” produces thousands of Web sites, many of which say that anyone can lose weight and build muscle through strength training, even doing routines that aren’t particularly strenuous.
Books like Kathy Smith’s “Lift Weights to Lose Weight” also perpetuate the myth that building muscle supercharges metabolism and quickly leads to weight loss. In “Smart Girls Do Dumbbells,” Judith Sherman-Wolin claims that resistance-training can “melt away those stubborn pounds you’ve been trying to lose all your life.” And Jorge Cruise’s best seller, “8 Minutes in the Morning,” advises readers to forget aerobics or grueling workouts because doing his two strength-building exercises a day “will help you firm up five pounds of lean muscle within the first few weeks, allowing your body to burn an extra 250 calories per day.” Ms. Woodworth of Seattle said, “Practically every fitness book and magazine I ever read said strength training boosts metabolism so you lose weight easier and faster.”
Before taking up weight lifting, she had already lost 15 pounds in about three months by cutting calories and walking and running for an hour three times a week. With 40 pounds still to shed, she turned to what she had heard was the magic bullet.
Her trainer advised her to lift four times a week, cut her cardiovascular exercise to less than 30 minutes but still keep dieting. After six weeks, she was frustrated to find she had gained two pounds. That added weight probably wasn’t muscle. Decreasing her high-calorie-burning walks and runs was the more likely culprit. Lifting weights burns few calories – “at least the way the average nonathlete does it and certainly the way most women tend to do it, using relatively low weights and few sets,” Dr. Donnelly said. The same time spent an aerobic workout could double the calorie burn.
Once Ms. Woodworth increased her time on cardio, she lost the added weight.
Proponents of the theory that weight lifting leads to weight loss argue that it is the long-term effect of gaining more muscle, which burns more calories at rest, that causes weight loss. Still, that has never been proven in studies.
Studies show that even women who do what it takes to get stronger develop only two to four pounds of muscle after six months of progressive lifting. Given that one pound of muscle burns between 7 to 13 calories a day (as determined by studies that measured oxygen and blood flow to tissues), that means the average boost in metabolism is only 14 to 52 calories a day, said Dympna Gallagher, the director of the body composition unit at the New York Obesity Research Center in Manhattan.
The effect of weight lifting “on metabolism is minor and certainly not the savior of dieters,” said William Kraemer, a professor of physiology and neurobiology at the University of Connecticut.
A recent yearlong study of 59 sedentary women at the University of Pittsburgh demonstrated what little difference weight training can make in weight loss. About a third of the women lifted weights three times a week, another third did yoga three times a week, and the last third did neither. All the women followed a daily diet of 1,200 to 1,500 calories for the entire year and walked five days a week. In the end, those who had lifted weights or practiced yoga lost as much weight and fat – but no more – than those who only dieted and walked.
Surprisingly, many of the women became no stronger. “We were looking at whether women would stick to the routine, and if so, would they resistance train intensely enough,” explained Kara Gallagher, the lead researcher. “It appears that many did not.”
When people lift light weights and fail to progressively increase the load, they only increase endurance, Dr. Kraemer said.
After turning “doughy,” Ms. Rivera of Los Angeles followed a few workouts using five-pound weights that she’d seen in Glamour and Shape magazines. “After three months the scale hadn’t budged,” she said. “I didn’t see much of a difference in muscle tone.”
Eventually she realized that light weights were not enough. “When I progressed from a five-pound dumbbell and began to lift heavier, my arms and butt got firmer within three weeks, although I still did not lose weight,” she said.
For those looking to build a more sculptured body, dieting may be counterproductive. “To create new muscle tissue you need to eat enough, not cut calories, to fuel the process,” said Karen Reznik Dolins, the director of nutrition at Altheus, a sports center in Rye, N.Y., and a nutrition adviser to the New York Knicks.
Genetics can also help determine the impact that weight lifting can have on muscle development and metabolism.
Researchers at the University of Massachusetts at Amherst looked at almost 600 men and women who did a strenuous, progressive resistance routine for three months, according to a study in this month’s Medicine & Science in Sports & Exercise. Three percent were “high responders,” some of whom doubled their strength. One percent were “low responders,” who became only 1 percent stronger than they were when they started. The majority of men and women increased muscle size 15 to 25 percent; and most men improved their muscle strength 40 percent while women increased theirs 65 percent.
Shannan Catlett, a fashion sales executive in Manhattan, said lifting heavy weights helped tone her slimmer body. After she lost 50 pounds by using the elliptical machine and treadmill and by following a healthier diet, she improved her muscle definition with weights.
“I never lost weight from strength training, but my butt got smaller and I got stronger and firmer all over,” Ms. Catlett, 41, said. “I still have to make sure that I’m always fit in regular cardio to maintain my weight.”
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