Is lifting weights better than cardio for weight loss?
Conventional wisdom says that aerobic exercise (combined with cutting calories) is the best way to lose weight. But millions of people have logged hours on ellipitical machines and stationary bikes without dropping any pounds. This means that either (a) losing weight takes a lot more effort than most people expect, or (b) we’ve been misled and there’s a much better way to lose weight. Strength training is often proposed as that “better way” – though the evidence strongly suggests the real answer is (a).
In a head-to-head match-up of an aerobic workout versus a strength workout, there’s no dispute that you’d burn more calories in the aerobic workout (assuming that intensity and duration are held roughly equal). It’s the calories you burn during the rest of the day that might tilt the field in favor or weights. A classic study published in 1977 showed that the gradual decline with age of your resting metabolic rate – the calories you burn just to stay alive, even when you’re sleeping – is due almost entirely to the loss of muscle mass that begins in your mid-30s and continues inexorably for the rest of your life. Pumping iron slows the loss of muscle, or even adds new muscle which keeps your metabolism ticking a little more quickly.
Strength training also stimulates your body to burn more fat instead of carbohydrate as fuel – though it’s not clear that burning more fat actually reduces the amount of fat you store in the long term. There’s also the simple fact that if you’re strong and healthy, you’re more likely to move around, lift things, climb stairs, and otherwise burn calories in the course of your day-to-day life. It was these factors that convinced the American College of Sports medicine, in 2009, to acknowledge the possibility that strength training might contribute to weight loss, reversing an earlier official stand. They’re now taking more of a wait-and-see approach – there’s’ no experimental evidence that these factors make any significant difference, but they at least sound plausible.
There’s no shortage of studies on strength training and weight loss. A typical example, published in the American Journal of clinical Nutrition in 2007, monitored 164 overweight, middle-aged women for two years. Half of them lifted weights twice a week, the other half were simply given brochures recommending aerobic exercise. The weights group gained about three pounds, including a 7 percent increases in dangerous abdominal fat; the control group gained 4.4 pounds, with a 21 percent spike in abdominal fat. This is clear evidence that strength training is god for you – but not that it’s better than aerobic exercise for weight loss.
The most positive results, not surprisingly, come from studies that combine aerobic and strength exercise. A Korean study that pitted a six-days-a-week aerobic training program against three days each of aerobic and strength training found that the combined program produced the best results for decreasing surface and abdominal fat, as well as increasing muscle mass. There’s’ not doubt that strength training has innumerable benefits – including, possibly, boosting your metabolism and fat-burning abilities. But for real-world health purposes, it works best in combination with aerobic exercise.