Lifting Weights to Lose Weight?

Q: I started lifting weights because I heard you can burn more calories from lifting than from doing cardio. Is this true? How long should I rest in between the repetitions before starting a new set?

A: There's a lot of confusion about exactly what lifting weights can do for you. One thing is for sure, if you're trying to lose weight, then doing more cardio activities—such as walking, running or using machines like the elliptical trainer—is the way to go.

Weight loss comes from using more calories than you take in. You can use more calories the fastest with activities that use your whole body over an extended period of time, as opposed to doing site-specific exercises that fatigue one particular muscle group or two. Any movement burns calories, but weight training burns calories relatively slowly—especially when it's a novice or recreational exerciser using relatively low weights and performing just a few sets. In contrast, you can double your calorie burn by spending the same amount of time doing an aerobic workout (depending on the intensity).

Walking briskly for 30 minutes will burn more calories than doing a half-hour's worth of biceps curls, ab crunches or shoulder raises, for example. If you are substituting cardio workouts with more muscle-based workouts such as body sculpting or Pilates, you will burn fewer calories over the week and that will slow down your rate of weight loss.

You can burn more calories during a weights workout by performing more lower-body moves such as squats and lunges, or doing a circuit-style routine where you move quickly through the routine and even insert cardio intervals such as jumping jacks or jogging in place in between exercises. There is some evidence that a very intense, super-hard weights workout can create a slight caloric afterburn. But typical exercisers simply don’t push themselves this much. So overall, cardio is more efficient at burning the most calories.

You will, no doubt, hear differently. And you will probably come across claims that dumbbells provide a magical solution. If you lift weights, the argument goes, you build muscle, which speeds up your metabolism so that you even burn more calories while you sleep.

But this is more hype than hope. Leading exercise physiologists conducted a comprehensive review of the research on exercise and weight loss for the American College of Sports Medicine and presented their findings at a 2003 conference. While resistance training was recommended for its beneficial role in potentially improving muscle, strength and power, they found no evidence that it enhanced weight loss, especially when combined with dieting.

One claim—that muscle weight burns more calories, and so adding muscle makes you burn more calories every day—may be true in theory. But, in reality, it's probably not making a big enough difference for most people. First, this effect may be less powerful than most people believe. Often the information about muscles and metabolism is misconstrued. A common claim is that every extra pound of muscle burns from 30 to 50 calories per day. Some sources cite that one pound of muscle can burn an extra 100 calories per day. This "fact" has been repeated by trainers everywhere, but few have bothered to investigate the actual research where these claims originated. 

In reality, one pound of muscle burns about seven to 15 calories a day, not 50, explains Dymphna Gallagher, the director of the body composition unit at the New York Obesity Research Center in Manhattan. So, if a person has managed to stick to a program lifting progressively heavier weights for a long enough stretch of time, they may accumulate enough extra muscle to boost their metabolism by about 14 to 30 calories a day—not several hundred, as is often claimed.

One of the foremost experts on the science of strength training concurs: "The effect on metabolism is minor and certainly not the savior of dieters," says William Kraemer, a professor of physiology and neurobiology at the University of Connecticut.

When it comes to dieting with weight training, dieting may thwart any possible effect. The body needs more calories than normal to build muscle. A person trying to cut back will have a harder time producing an anabolic effect in their body where it grows new muscle tissue.

That's not to say that lifting weights won't help you get stronger, firmer and healthier. It will. But it just isn't the place to focus if you are trying to shed lots of weight. You can develop more stamina from lifting weights, which in turn may help you last longer during cardio workouts—so, definitely include one to three sessions a week of weight training into your routine for this purpose. But to burn calories, do cardio more often and for longer periods.

As far as how long to rest between sets, how long you wait depends upon your goal, as well as how much weight you're lifting and how many reps and sets you're doing. Between-set breaks usually last anywhere from 30 seconds to 5 minutes. Unless you are lifting very heavy weights, you can shorten the rest periods. Rest intervals of about a minute in between sets are more effective at increasing strength than a shorter interval. But different exercises may require different durations. A good gauge is to aim for about one minute and make sure your muscles feel like they have recovered in between sets.

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Martica is a Manhattan-based exercise physiologist and nutritionist and an award-winning fitness instructor. She has written for a variety of publications including Self , Health , Prevention , The New York Times and others. Martica is the author of seven books, including her latest, - Cross-Training for Dummies . (Read her full bio.)