早稲田商2010 III

You have heard it for years: to lose weight, go to the gym. But while physical activity is crucial for good health, it doesn't always melt off the weight ―in fact, it can add some. Here is why.

One of the most widely accepted, commonly repeated assumptions in our culture is that if you exercise, you will lose weight. I exercise all the time obsessively, but my weight remains the same 74 kg it has been most of my adult life. I still have stomach fat that hangs over my belt when I sit. Why isn't all the exercise wiping it out?

The basic problem is that while it is true that exercise burns calories and that you must burn calories to lose weight, exercise has another effect: it can stimulate hunger. That causes us to eat more, which in turn can negate the weight loss benefits we just acquired. Exercise, in other words, does not necessarily help us lose weight. It may be even making it harder.

People who regularly exercise are at significantly lower risk for all manners of diseases ― those of the heart in particular. They less often develop cancer, diabetes and many other illnesses. In addition, exercise improves your mental health and cognitive ability. A study found that older people who exercise at least once a week are 30% more likely to maintain cognitive function than those who exercise less. But the past few years of obesity research show that the role of exercise in weight loss has been widely overstated.

After we exercise, we often yearn for sugary calories like those in muffins or in sports drinks. A standard bottle of sports drink contains 130 calories. If you are hot and thirsty after a 20-minute run in summer heat, it is easy to drink that bottle in 20 seconds, in which case the calorie output and the calorie intake are probably the same. From a weight loss perspective, you would have been better off sitting on the sofa knitting.

Ultimately, the problem is about not exercise itself but the way we have come to define it. Many obesity researchers now believe that very frequent, low-level physical activity ―the kind humans did for tens of thousands of years before the leaf blower was invented ―may actually work better for us than the occasional bouts of exercise you get as a gym member.

In short, it is what you eat, not how hard to try to work it off, that matters more in losing weight. You should exercise to improve your health, but be warned: intense spurts of vigorous exercise could lead to weight gain.