ACSM analysis of runners finds weakened relationship between diet and body mass index
INDIANAPOLIS – While Thanksgiving is notoriously a diet-buster for U.S. adults concerned with weight, there may be one segment of the population who can ease their guard a bit this holiday. New ACSM research indicates that runners who log more than two kilometers per day may be somewhat immune to the effects of at-risk diets.
Paul Williams, Ph.D., a researcher with the Lawrence Berkeley National Laboratory, categorized 106,736 runners by the distance they run each day – fewer than two kilometers, two to four kilometers, four to six kilometers, six to eight kilometers and more than eight kilometers. In the least active group (fewer than two kilometers per day), a runner’s body mass index and waist circumference increased significantly in association with higher meat intake and lower fruit intake. In the most active group (more than eight kilometers per day), the estimated effects of diet on body mass index and waist circumference were reduced by 50 percent or more. Men and women who ran more than two kilometers per day did reduce the effects of diet on body weight, but their reductions were not as great.
“Generally, body mass index and waist circumference increase as a person eats more meat and less fruit,” said Williams, the author of the analysis. “My analysis indicates that this relationship weakens as runners increase their daily mileage. It appears that the more miles a person logs each week, the less affected they are by variances in their diet.”
Williams explains that this could, in part, be due to the enhanced fat burn that comes with exercise. It could also be due, in part, to improved coupling between energy intake and expenditure. Runners who exercise more may be better at balancing their diet.
“My observations suggest that runners who exceed the recommended Physical Activity Guidelines for Americans can reduce their risk of gaining weight from high-risk diets, those with high meat and low fruit content,” said Williams. “We have other data suggesting this benefit may also apply to walking.”
Data were collected through the National Runners’ Health Survey, a two-page questionnaire sent to running magazine subscribers and race participants. The questionnaire collected demographic, running history, weight history, diet, cigarette use, health history and medication information from each runner. Results indicate that higher mileage runners tend to be younger and slightly more educated, eat less meat and more fruit, and – if male – drink less alcohol.
Though Williams was able to draw a strong conclusion from his investigation, he warns that the cross-sectional nature of the analysis prevents us from drawing a causal inference between running distance, diet and adiposity.
The study, “Exercise Attenuates the Association of Body Weight with Diet in 106,737 Runners,” is published in this month’s issue of Medicine & Science in Sports & Exercise®, the official journal of ACSM.
The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 45,000 international, national and regional members and certified professionals are dedicated to advancing and integrating scientific research to provide educational and practical applications of exercise science and sports medicine.
Medicine & Science in Sports & Exercise® is the official journal of the American College of Sports Medicine, and is available from Lippincott Williams & Wilkins at 1-800-638-6423. For a complete copy of the research paper (Vol. 43, No. 11, pages 2120-2126) or to speak with a leading sports medicine expert on the topic, contact the Department of Communications and Public Information at 317-637-9200 ext. 133 or 127. Visit ACSM online at www.acsm.org.
The conclusions outlined in this news release are those of the researchers only, and should not be construed as an official statement of the American College of Sports Medicine.