Critiquing Cardio Workouts
Trainer Jim Karas says it's better instead to lift weights
Is it the couch potato's dream come true? Personal trainer to the stars Jim Karas's new book, The Cardio-Free Diet, promises you can unplug the treadmill and still lose weight. In fact, he says, cardiovascular exercise may actually hurt your efforts to drop a few pounds. Instead, Karas advocates a less time-consuming strength-training routine of simple lifts and presses with either free weights or rubber tubing. Is he right? Here's an assessment of his thesis:
Traditional cardiovascular exercise has been vastly oversold as a way to lose weight. Walking, running, spin classes "do not burn up nearly as many calories as we've been led to believe," says Karas. Moreover, he says, cardio makes you so hungry that you overeat. People definitely overestimate the caloric burn from working out and underestimate how much they eat, and that can mean weight gain, says JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital and author of The 30-Minute Fitness Solution. But she says many people report fewer hunger pangs after a workout.
Strength training provides the same benefits of cardio-in less time. Karas says cardio requires too much time and can pound your joints into disrepair. His alternative: a strength-training program that he argues not only builds muscle but can get the heart pumping, both because of the exertion of lifting and because people are supposed to move quickly from one exercise to the next. But while there is a mountain of evidence showing that cardiovascular exercise is good for your heart, simply lifting weights-even when it's done quickly enough to get your blood pumping-doesn't provide the same benefits, says Cedric Bryant, chief science officer of the American Council on Exercise, a nonprofit fitness certification and education group. "You're not engaging a significantly large amount of muscle mass in an extended fashion," he says. You don't have to run a marathon to get that heart benefit: Thirty minutes a day of brisk walking will do it.
A strength-training routine of as little as 60 minutes a week can help you drop weight. Karas says his routine builds muscle, changes your body shape, and helps you lose pounds. It's a three-day-a-week program that starts small-10 different exercises that may take as little as 20 minutes to do-and builds over time. But the "diet" part of The Cardio-Free Diet is just as important. Women begin at 1,200 calories a day and top out, after several weeks, at 1,500 calories; men start at 1,500 calories and go up to 1,800. That is far less than most people consume. So people who stick to his program are bound to lose weight.
The bottom line: Absent the same kind of evidence that cardio is good for the health of your heart and other bodily systems, it's not a great idea to totally sub strength training for cardio. The ideal exercise routine, says Manson, includes both, since strength training is definitely important for building muscle, maintaining bone density, and goosing your metabolism. If you're aiming to lose weight, you've got to follow the basic equation that everyone agrees on: Burn more calories, through exercise or everyday activity, than you take in.
This story appears in the May 14, 2007 print edition of U.S. News & World Report.