We hear a lot that a little exercise is the key to weight loss – that taking the stairs instead of the elevator will make a difference, for instance. But in fact it’s much more efficient to cut calories, says Samuel Klein, MD at Washington University’s School of Medicine. “Decreasing food intake is much more effective than increasing physical activity to achieve weight loss. If you want to achieve a 300 kcal energy deficit you can run in the park for 3 miles or not eat 2 ounces of potato chips.” It’s as simple as that. Some studies have borne out this dichotomy, pitting exercise against diet and finding that participants tend to lose more weight by dieting alone than by exercise alone. Of course, both together would be even better.
The problem is that when you rely on exercise alone, it often backfires, for a couple of reasons. This is partly because of exercise’s effects on the hunger and appetite hormones, which make you feel noticeably hungrier after exercise. “If you walk briskly for an hour and burn 400 kcal,” says Klein, “and then have a beer and a slice of pizza afterwards because the exercise made you feel hungry…you will eat more calories than you have burned.” It may not always be beer and pizza, but people do tend to naturally compensate for the calories they expend.
“This is an adaptive system,” adds David Allison, PhD. “For every action there’s a reaction; that’s a law of physics, not of biology, but it seems that it also works in biological systems. This is why we often overestimate quite radically an effect of a particular treatment.” He points out that public health campaigns that, for example, urge people to take the stairs instead of the elevator or go on a nightly stroll – or, for that matter, even eat fewer calories – are unlikely to work, since they may fail to take into account the body’s compensatory mechanisms that can totally counteract the effect.
The other problem with exercise-without-dieting is that it’s simply tiring, and again, the body will compensate. “If the exercise made you tired so that you become more sedentary the rest of the day, you might not experience any net negative energy,” says Klein. Some of the calories we burn come from our basic movements throughout the day – so if you’re wiped out after exercise, and more likely to sit on the couch afterwards, you’ve lost the energy deficit you gained from your jog. Click here
posted @ Sunday, October 30, 2016 2:01 PM