Very often, fitness professionals recommend weight training as a primary means for weight loss. While theoretically weight training could be effective in facilitating weight reduction, it may not be as effective as is sometimes presented. By far, the greatest contributor to the total calories we burn each day is our resting metabolism simply because rest is where we spend most of our time. Resting metabolism is the result of the biological processes necessary to keep our cells, and therefore us, alive. The biggest contributor to resting metabolism is skeletal muscle, and that is where the weight training for weight loss theory emanates. If we, in fact, significantly increase our muscle mass and resting metabolism, we could increase the amount of calories burned each day. The question I ask is, what kind of time will it take in a weight room to get significant gains in muscle size, and is this the best use of the exercise time we have when the overall goal is weight loss?
Most of us are not going to see significant gains in muscle size by following the basic recommendations for strength training (i.e., 2-3 days a week, moderate to heavy weights, for 8-12 reps on 8-10 different exercises). Women, in particular, won’t usually see substantial increases in muscle size simply because they don’t have the muscle composition or hormonal support for it. Even though we may realize gains in strength, this does not always result in gains in muscle size. Many of the initial strength gains are a result of neural improvement and not the result of increased muscle fiber size. It’s not to say that we can’t increase muscle size, but for most of us, this will take a lot of time in the weight room. I believe that time would be better spent performing aerobic activity and closely monitoring our diet.
There is no question that weight training should be a part of a weight loss program. It simply shouldn’t be used as the center piece. Supplementing aerobic exercise and caloric restriction with strength training helps preserve muscle mass and therefore resting metabolism. Preserving muscle mass is very different from increasing muscle mass and can be achieved with much less strength training.
The American College of Sports Medicine (ACSM) and the American Heart Association (AHA) have both taken research-based positions on weight training for weight loss. Both say the evidence is equivocal at best. You can review both documents below.