Are the Benefits of Exercise Overblown?

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Are the benefits of exercise overblown? That is the question being asked by Susan B. Roberts in her recent article, The Exercise Myth. Here are a few choice excerpts…

The drumbeat of get moving to lose weight has gotten so loud that almost everyone blames his or her weight problem on not spending enough time at the gym.

But a hard look at the evidence just doesn’t support the hype. The inconvenient truth is that we now eat about 500 more calories per day than we did 30 years ago. That’s enough to explain our growing waistline without any need to factor in exercise.

Combine this fact with national surveys showing that people who do manual occupations—jobs like construction, farming, and domestic work—are heavier than people who sit in front of a computer screen all day. Indeed, these physically strenuous jobs carry a 30% increased risk of obesity when compared to office jobs. Of course, comparisons like this don’t factor in social class, or whether you eat brownies, or take a run after work, but that’s the whole point—compared to factors like what we eat and what our education level is, hard manual labor just doesn’t make as much of a difference. Even if your day is spent shoveling gravel, you’re still going to find yourself with a pot belly if you’re always lunching on pizza and soda.

The evidence isn’t just anecdotal. My lab at Tufts University summarized 36 years of published studies on exercise and weight, conducted between 1969 and 2005. What we found would frustrate anyone spending upward of $800 a year on a gym membership to lose weight. The averaged results of the studies showed that an hour of exercise per day results in an average fat loss of just six pounds over the course of several months—hardly the benefit one would expect from all that work. Perhaps more importantly, most of the studies only managed to get people to exercise 30 minutes a day, which is the maximum most people have the time and inclination for, at which point the average weight loss goes down to a meager three pounds. It is true that some of the studies showed greater fat losses than the average, but just as many showed less.

Research doesn’t have good answers to the question of why exercise doesn’t work for the average person as well as it seems it should, but I suspect the reasons are increased hunger (you eat almost as many extra calories as you burn) and reduced energy expenditure at other times (exercise may make you more relaxed and less fidgety). So, you end up fit, healthy, and less stressed out, but wondering why you still have pounds to lose.

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