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Eat Less or Move More?

By Greta Guest

People setting a goal to lose weight in 2013 may want to first ask themselves if diet or exercise is more important to success.

Whether a person believes obesity is caused by overeating or by a lack of exercise can predict whether he or she will gain or lose weight, according to new research to be published in the journal Psychological Science. The paper is titled “Lay Theories of Obesity Predict Actual Body Mass.”

With two-thirds of the adult U.S. population classified as overweight or obese and similar numbers in many developed nations, obesity has become an important health concern.

In a series of studies across five countries on three continents, the research showed people mainly believe either obesity is caused by a lack of exercise or by a poor diet.

“The greater the extent to which you believe it is diet, the thinner you are on average,” says Brent McFerran, a marketing professor at U-Ms’ Ross School of Business.The beliefs a person holds predict how that person will approach the goal of weight loss. McFerran says people who believe obesity is caused by diet consume less food. Those who believe it is caused by a lack of exercise should work out more. The problem with that is people tend to overestimate the amount of calories burned during exercise and underestimate total calories in the food they eat.

For example, a 20-ounce venti Java Chip Frappucino from Starbucks contains 580 calories. It would take the average person four hours to walk it off. (For more on calories ingested and energy expended, see this month’s Health Yourself column.)

This is not to say exercise does not help reduce weight as long as calorie intake doesn’t also increase, says co-author Anirban Mukhopadhyay, a marketing professor at the Hong Kong University of Science and Technology.”Our finding is simply that people who believe strongly in lack of exercise as the primary cause, rather than poor diet, tend to have higher body masses.” Mukhopadhyay says.

Food for thought.

Greta Guest

Greta Guest

GRETA GUEST is a senior public relations representative at Michigan News, the central news service at the University. She handles media relations and outreach for U-M's Ross School of Business, Ford School, and U-M Tech Transfer. Guest writes about faculty research, tech start-up acquisitions, and news from these areas. She also produces Policy Points videos for the Ford School. Guest joined the university in 2012 after a 20-plus year journalism career with writing and editing posts at the Detroit Free Press, the Macomb Daily, the Associated Press, and Werner Publishing in Los Angeles. Her work has appeared in newspapers around the world. A series of her real estate stories won a Society of American Business Editors and Writers best in business award in 2010. She has experience covering politics, business, Detroit's casinos, breaking news of all types, real estate, and retail. Follow her on Twitter: @gretaguest.


  • Anthony Cece - 1996

    Four hours for the average person to burn off 580 calories? How much does this average person weigh and how slowly is it assumed this person walks? This stat seems quite conservative.


  • bernhard muller - 1964

    I recall seeing how shocked I was how few calories I had burned after a vigorous hour on a sophisticated exercise machine.


  • Caroline Richardson

    Perhaps dieters weigh less because they have less lean muscle mass than exercisers.


  • Michael Craven

    Thank you for that interesting information. It looks like both diet and excercise play a key role in staying healthy.
    Michael C Craven
    Chicago Divorce lawyer