Diet Beats Exercise for Weight Loss

After decades of weight loss research, experts conclude that exercise alone won't win the battle of the bulge.


Exercise can be a powerful balm for many of the things that ail us, including depression, bone loss, fatigue, heart disease, diabetes and arthritis. But the reason many of us pound the pavement is because we want to lose weight, and that, experts say, is a goal for which exercise alone may not be especially helpful. 

Monitoring your diet – specifically portion control – is more effective than exercise for weight loss. The reason boils down to simple math. It is far easier to eat 100 calories – the amount in a piece of bread – than it is to burn them off, which, for most of us, would require walking one mile. And while exercise helps us burn more calories, it also increases appetite, making it excruciatingly easy to undo all that hard work.

In the position paper “Physical Activity and Public Health: Updated Recommendations for Adults from the American College of Sports Medicine and the American Heart Association” which was published in 2007, a blue ribbon panel of experts reviewed all available scientific evidence on the connections between exercise and health and conceded that while exercise is critical for many aspects of health, it doesn’t seem to help with weight loss.

“Despite the intuitive appeal of the idea that physical activity helps in losing weight,” the panel wrote, “it appears to produce only modest increments of weight loss beyond those achieved by dietary measures and its effects no doubt vary among people.”

Amy Luke, PhD, a nutritional epidemiologist at Loyola University, Stritch School of Medicine, in Chicago, has seen this phenomenon for herself. 

Luke compared two populations of black women: One group was from rural Nigeria, while the other was from downtown Chicago. All body size measurements were lower in the Nigerian women, and Luke and her team set out to understand why.

“Our hypothesis going in was not particularly brilliant,” Luke says. “It was that women who were heavier, particularly in the U.S., would have lower calorie expenditure than women who had a lower body mass index (BMI).” (To calculate your BMI, click here.)

In other words, she thought thin women would be more physically active than obese women. That turned out not to be the case. “The differences in physical activity were minimal,” Luke says.

Luke believes the Chicago women weigh more than their Nigerian counterparts because of differences in diet. The Chicago diet is 40 to 45 percent fat and high in processed foods, while the Nigerian diet is high in fiber and carbohydrates, and low in fat and animal protein.

“For us, the take-home message is that a lot of public health policy on increasing physical activity for weight control may not be as productive as focusing on the dietary intake side of things,” says Luke, whose study was published in the journal Obesity.

In the real world, people who have lost significant amounts of weight and kept it off say they have used a combination of exercise and diet to achieve their goals. Ninety-eight percent of people enrolled in the National Weight Control Registry, a group of 5,000 individuals who have lost at least 30 pounds and kept it off for at least one year, report modifying their food intake in some way to lose weight, while 94 percent say they increased their physical activity.

The trick, experts say, is to carefully monitor how much you’re eating, by counting calories, watching portion sizes or keeping a food journal, while increasing your physical activity. While you’re fighting flab by cutting calories, you can still appreciate exercise for all the things it does to well, such as relieving joint pain, fatigue, boosting mood and helping to keep your heart and bones strong.

“It’s critically important for those things,” Luke says, “but for weight loss per se, it may not be as critically important as we’ve stressed.”

Don't hang up your walking shoes quite yet though – physical activity  is a proven effective way to treat the aches and pains that come with arthritis.


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