Study: Less than 10 minutes of higher-intensity physical activity reduce risk of obesity

Short bursts of less than 10 minutes of higher-intensity physical activity reduce the risk of obesity, finds a new study in the American Journal of Health Promotion.

"This research shows that when it comes to maintaining a healthy weight, every little bit of exercise counts, as long as it's of reasonable intensity, such as a brisk walk, climbing stairs or jumping rope," said study author Jessie X. Fan, Ph.D., professor in the department of family and consumer studies at the University of Utah.

Little bursts of exercise can add up to have a significant impact on a person's weight, said Fan. In fact, the study showed that every minute spent in short bouts (1-10 minutes length) of high-intensity activity was as beneficial to Body Mass Index (BMI) as every minute in longer bouts (10 or more minutes) of higher-intensity exercise. The study found that lower-intensity bouts of activity, of either short or long duration, were not associated with a lower BMI or risk of overweight or obesity in men or women.

The study's authors noted that people often struggle to find the recommended 10-to-30 minute blocks of time that have been prescribed to meet widely held recommendations for exercise. The current guidelines from the U.S. Department of Health and Human Services recommend that adults get 150 minutes weekly of moderate-to-vigorous physical activity, accumulated during bouts lasting at least 10 minutes each. However, the researchers note, fewer than 4 percent of Americans age 20 to 59 reach this guideline.

The new study involved a nationally representative sample of 4,511 Americans aged 18 to 64 from 15 counties across the country. Participants wore accelerometers that measured their steps and the intensity of their steps for 7 consecutive days.

The authors reported that for both men and women, the most minutes of physical activity were accumulated in shorts bouts of low intensity activity, followed by short bouts of higher intensity activity, then by long bouts of low intensity and lastly by long bouts of high intensity. In other words, short bouts of physical activity represent the bulk of the activity most Americans experience. The findings underscore the notion that for maintaining a healthy weight, the authors write, "every brisk minute counts!"

Jennifer Gay, Ph.D., assistant professor of health promotion and behavior at the University of Georgia explained that the guidelines setting a 10-minute minimum for an exercise session to "count" had been chosen because 10-minute bouts represent the point at which the body starts to experience benefits to the heart and lungs. This new study, she said, focused on the impact of short-versus-long bouts of activity on people's weight, which reflects how many calories they burn compared to the number they consume. Gay noted that, "both cardiorespiratory health and energy expenditure can contribute to reductions in disease risk."