This question seems to get asked and answered every couple of months in the fitness world. The most recent research on the topic, however, seems to be the most definitive: According to a study published last month in the Journal of Applied Physiology, aerobic exercise trumps weight lifting in terms of burning fat and losing weight, especially if you only have limited time to work out.
Researchers from Duke University Medical Center found that a group of overweight study participants who did 45 minutes of cardio three times a week lost more weight than those who spent about the same amount of time lifting weights, instead. They also lost about the same amount as a third group that did both types of exercises each week, which took twice as long.
The study is the largest to date to directly compare the effects of the two different types of exercise on body composition, say the authors, and the results did come as a bit of a surprise: Previous research has suggested that strength training—done either with free weights, weight machines, or with the body’s own resistance—boosts metabolic rate, which, in turn, helps fuel fat burn.
While that may be true, the researchers say, the effects weren’t significant enough to have real weight-loss benefits. Given these results, they wrote, “It may be time to seriously reconsider the conventional wisdom that [resistance training] alone can induce changes in body mass or fat mass due to an increase in metabolism in overweight or obese sedentary adults.”
The strength-training and combination-workout groups did gain strength and lean muscle mass, which the authors acknowledge are important for overall health.
THE BOTTOM LINE: If you have the time, a routine that combines both cardio and strength training is still probably the best for improving your overall fitness. But if weight loss is your top priority and you only have time for one or the other, pounding the pavement beats out bench pressing.