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Exercise more effective than diet at keeping weight down, study suggests

Exercise more effective than diet
REUTERS/Rick Wilking
After analyzing the data, the researchers found that moderate-to-vigorous exercise had a significant inverse relationship to BMI and waist circumference in both men and women and across all age groups — except those in their 20s.

Physical activity has more impact on our weight (and waistline) than diet, particularly as we grow older, according to a new study.

This finding may explain, in part, why most people gain weight in middle age even though they tend to eat more healthful foods than they did when they were younger.

For the study, researchers at the University of South Carolina analyzed data collected from almost 5,000 adults aged 20 to 70 who participated in the National Health and Nutrition Examination Survey (NHANES) between the years 2003 and 2006. In addition to providing information on their weight, body mass index (BMI), waist circumference and dietary choices, the participants also wore an accelerometer for seven consecutive days to measure their physical activity.

After analyzing the data, the researchers found that moderate-to-vigorous exercise had a significant inverse relationship to BMI and waist circumference in both men and women and across all age groups — except those in their 20s.

In other words, the more physically active people were, the less body fat they had, including around their waist.

The quality of the participants’ diets, however, was not consistently associated with a lower BMI or smaller waist circumference, with one demographic exception: people in their 50s. 

The results held even after adjusting for such factors as race, ethnicity, marital status, education level, and whether or not the participants smoked.

“We believe that these findings provide support for public health efforts to prevent obesity by promoting increased physical activity in adult Americans,” the authors conclude.

Excess body fat, especially abdominal fat, is, of course, a risk factor for a variety of serious medical conditions, including type 2 diabetes and heart disease. 

Caveats

This study, like all studies, has its limitations. It relied on the participants’ own reports of their dietary habits, for example, and on only a week of physical activity data.

Still, the findings are robust enough to underscore the importance of being physically active throughout our lifetimes. 

“Americans should meet the federal physical activity guideline, 150 minutes of moderate-intensity physical activity per week,” Tate told the Huffington Post. "If most American adults met that guideline, rates of overweight and obesity would be substantially lower than they are today."

(You may want to include some vigorous physical activity every week, according to another study published this month.)

The current study appears in the April issue of the journal Medicine & Science in Sports & Exercise. It can be downloaded and read in full through the journal’s website.

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