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Beliefs on Weight Loss Can Torpedo New Year's Resolutions

1/4/2013 --

People who believe obesity is caused mainly by diet are thinner than those who think the cause is lack of exercise.

ANN ARBOR, Mich. — 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 from Ross marketing professor Brent McFerran.

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. But opinions vary on the best way to combat the epidemic.

In a series of studies across five countries on three continents, McFerran's research showed that people mainly believe either that 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 McFerran, the Arnold M. & Linda T. Jacob Assistant Professor of Marketing. The paper, "Lay Theories of Obesity Predict Actual Body Mass," will be published in the journal Psychological Science.

McFerran argues that the beliefs a person holds predict how he or she will approach the goal of weight loss — people who believe obesity is caused by diet consume less food, while those who believe the cause is lack of exercise should work out more. The problem is that people tend to overestimate the amount of calories burned during exercise and underestimate 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.

The study does not diminish exercise's role in helping 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 [for weight gain], rather than poor diet, tend to have higher body masses."

Read the study.

— Greta Guest

For more information, contact:
Greta Guest, 734-936-7821,