Jim Karas Says You Can Skip the Aerobic Workout
It sounds like a couch potato's dream: Personal trainer Jim Karas's new book, The Cardio-Free Diet, promises you can lose weight without lengthy sessions on the treadmill. In fact, he says, intensive cardiovascular exercise may actually be hurting your efforts to drop a few pounds and even damaging your health. Instead, Karas advocates a far less time-consuming strength-training routine of simple lifts and presses with either free weights or rubber tubing. Is he right? Here's a dissection of his thesis, point by point:
Cardiovascular exercise as a key to weight loss has been vastly oversold.
The usual recommendations–walking, running, spin classes at the gym–"do not burn up nearly as many calories as we've been led to believe," says Karas. Moreover, cardio makes you so hungry that you overeat. It's true that people have consistently been shown to overestimate the caloric burn from working out and to underestimate how much food they eat. That combination may mean weight gain, says JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital and author of her own fitness book, The 30-Minute Fitness Solution. But she notes that it's not universally true that exercise means a heartier appetite; many people report fewer hunger pangs after a walk or a bike ride.
Cardiovascular exercise is bad for your health in other ways.
Karas cites studies showing that intense exercise can depress the immune system and pound your joints into disrepair. His alternative: strength training, which he argues can get the heart pumping at the same time as it builds muscles, without the harm. But, while there is a huge body of evidence showing that cardiovascular exercise is good for your heart, there's not much evidence that strength training can provide the same benefit, says Manson. You don't have to run a marathon (which has been shown to temporarily depress immune function) or work out for hours to get that heart benefit: 30 minutes a day of brisk walking will do it.
The key to weight loss is a strength-training routine that can take as little as 60 minutes a week.
Karas's routine, he says, can build muscle, change your body shape, and help you drop weight. 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 then builds over time. It may well do all that–but the "diet" part of The Cardio-Free Diet, built around lean protein, high-fiber carbs, and "good fats" like nuts and olive oil, is just as important. And it's probably a big reason that his clients have seen such impressive weight loss. Women start out 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 are eating. So people who stick to his program are bound to lose weight. Can that be attributed to Karas's strength routine? It's hard to prove that.
The bottom line: Absent the same kind of evidence that suggests cardio is good for the health of your heart and other systems, it's not a great idea to totally replace it with strength training. The ideal routine, says Manson, includes both, since strength training is key for building muscle, maintaining bone density, and possibly goosing your metabolism to burn more calories. And if you're aiming to lose weight, you've got to follow the basic equation that both agree on: Burn more calories, through exercise or everyday activity, than you take in from food. If you hate the treadmill and don't mind restricting calories, Karas's plan, plus a half-hour of fast walking a day, might be a sensible prescription. If you'd rather eat more, figure out exactly how many minutes on the bike or StairMaster you need to compensate for your extra calories, and go for the burn.
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