Exercise for Weight Loss: Is Less More?

Anyone who thinks they know anything about exercise and weight loss is prone to regular shocks, based on a steady stream of surprising studies and reports. For example, a new one from the American Journal of Physiology concludes that 30 minutes of exercise a day is good, and 60 minutes less good.

Huh? And I thought I sailed through 5th-grade math with a passing grade.

A little recent context first. Although the study wasn't researching weight-loss per se when it was published 17 months ago, it opened lots of eyeballs. The study found that a vigorous 45-minute workout burned an extra 190 calories in the 14 hours post-exercise. This seemed simple enough--doing a few sprints or strides at the end of workouts to rev up the engine, and turn on the after burn made sense.

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A FAQ based on a more recent report from the outstanding Pennington Biomedical Research Center and the frighteningly named Center for Quantitative Obesity Research found that the relationship between exercise and weight loss is, well, frighteningly quantitative.

Not just that. But another new field study says that the super-skinny Hadza hunter-gatherer tribe of Tanzania doesn't actually move around more than big-bellied Westerners. The clear message from the Hadza: We don't need to exercise more; we just have to starve ourselves.

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The American Journal of Physiology study put sedentary, young male subjects in different groups for 13 weeks: one group maintained its sedentary behavior, one began exercising 30 minutes a day, and one 60 minutes a day. There was no statistically significant difference in weight or fat loss between the two exercise groups (both lost roughly 6-7 pounds), but all the trend lines favored the 30-minutes group, not the 60-minutes group. The investigators concluded: "A moderate dose of exercise induced a markedly greater than expected negative energy balance, while a higher dose induced a small ... compensation."

So what can be concluded from all of the above? We certainly need more studies, but until then, keep exercising and keep looking for ways to cut 100 calories a day from your current intake. (Try these 10 Ways to Boost Your Workout for Weight Loss)

--By Amby Burfoot, Runner's World

More from Runner's World:

Know When to Take Your Workout Up a Notch

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14 Reasons Why Your Weight Loss Plan Isn't Working