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Carolyn Hax

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Posted at 07:00 AM ET, 07/06/2012

Why diets don't work

We’re never going to beat obesity if we rely on food restriction as a prime means of losing weight.

That’s the considered opinion of Jim Hill, an obesity expert whose paper “Energy Balance and Obesity” published July 3 in the American Heart Association journal Circulation argues that curbing intake of food and calories to lose weight without also boosting physical activity is misguided and bound to fail.

Hill, professor of pediatrics and medicine at the University of Colorado Anschutz Medical Campus and co-founder of a national registry of people who have lost weight and kept it off, said in a phone interview, “We continue to promote the message to eat less, but that’s never been shown to work without increasing physical activity.”

The paper notes that two-thirds of U.S. adults and one-fifth of children and teens are overweight or obese and that we have, as a nation, become increasingly sedentary over the past century. Reversing that trend by promoting more physical activity could go a long way toward shrinking our collective waistline, Hill suggests.

We also need to be aware of the changes in physiology that occur when we cut back on calories, the paper notes. When we strictly reduce our calorie intake, our body tries to preserve pounds by slowing the rate at which it burns calories. And as anyone who has tried to lose weight just by eating less has been frustrated to learn, our smaller-size bodies require FEWER calories than they did when they were larger, so we have to restrict our intake even farther. That’s when we start feeling starved and defeated.

Hill invites us to imagine a different scheme in which we’re moving our bodies a lot more every day, so they actually require more calories to support that added physical activity. When we do that, our bodies get in the habit of burning calories more readily. “Physical activity does more than burn calories,” Hill says. “It puts the body in that zone where it’s going to work for you, not against you.”

The goal of this approach, Hill says, is to “maintain your weight by eating as many calories as you can. It’s positive. You’ll feel good. You get to eat more, not less.”

When we move into that zone, he suggests, we can eat more freely so we don’t feel frustrated. Of course, he says, we also have to eat “smarter,” choosing foods, for instance, that have lots of bulk to fill us up but don’t contain lots of calories.  And while we can enjoy a broad range of foods under this approach, Hill cautions that we should keep an eye on portion size so we don’t end up inadvertently eating more than our bodies require for fuel; those extra calories are stored as fat.

The paper maintains that it’s easier to prevent weight gain than to lose weight once it’s gained, as our bodies favor gaining weight over losing it.

Hill says education efforts are needed to help people understand the concept of “energy balance,” in which calories consumed match calories expended and/or stored. Employing that concept in our everyday lives requires cognitive skills, “just like managing a bank account,” Hill says.

The beauty of learning to manage our own energy balance, Hill explains, is that it allows us to make informed choices about what we eat.  Most of us might find we can afford to super-size our order of fries, he says, if we’ve gone for a long run earlier in the day — but not if we’ve been sitting on our butt all day.

What do you think of Hill's approach? Is the concept of “energy balance” new to you?

By  |  07:00 AM ET, 07/06/2012

Tags:  diets, weight loss

 
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