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ProSource: October 2013

Super-short Exercise Bouts (at the Right Intensity) Offer Big Weight-loss Benefits

When it comes to losing weight—or not becoming overweight in the first place—every little bit of exercise can help. New research suggests that micro-bouts of activity—shorter than 10 minutes—can lower one’s risk of obesity as long as the intensity level is sufficiently high. Furthermore, those who focused on shorter bouts were much more likely to meet or exceed the recommended 150 minutes of physical activity per week.

The study, published in the American Journal of Health Promotion, found that even brief episodes of physical activity that exceed a certain level of intensity can be just as effective in helping people control their weight as does the current recommendation of 10 or more minutes at a time.

The Study

Subjects for the study were drawn from the National Health and Nutrition Examination Survey (NHANES), a national program that has been collecting health and nutrition data from a representative sample of adults and children in the United States since 1999.

From 2003 to 2006, participants in the survey wore accelerometers for seven days, which captured data on their physical activity. This information was in addition to the broad range of demographic and health-related information collected in the NHANES program from interviews and physical examinations.

For this study, participants that were ages 18 to 64 years were drawn from the database. There were some exclusions, including pregnancy or impairments that compromised participants’ ability to walk, such as being wheelchair bound. The final sample size for the study was 2,202 women and 2,309 men.

Researchers compared measurements of physical activity based on length of time and intensity. Four categories were created:

  • Higher-intensity bouts (greater than 10 minutes exertion at greater than 2,020 counts per minute, or CPM)
  • Higher-intensity short bouts (less than 10 minutes at greater than 2,020 CPM)
  • Lower-intensity long bouts (greater than 10 minutes and less than 2,019 CPM)
  • Lower-intensity short bouts (less than 10 minutes and less than 2,019 CPM)

The study used body mass index (BMI) to measure weight status. A BMI between 18.5 and 24.9 is considered normal weight, whereas a BMI between 25 and 29.9 is overweight; and over 30 is obese.

Results showed that for women, each daily minute spent in higher-intensity short bouts was related to a decrease of 0.07 BMI. Looking at it another way, each such minute offset the calorie equivalent of 0.41 pounds. This means that when comparing two 5' 5" women, the woman who regularly adds a minute of brisk activity to her day will weigh nearly a half-pound less. Results were similar for men. Importantly for both, each daily minute of higher-intensity activity lowered the odds of obesity—5 percent for women, and 2 percent for men.

“What we learned is that for preventing weight gain, the intensity of the activity matters more than duration,” says Dr. Jessie X. Fan, professor of family and consumer studies at the University of Utah. “This new understanding is important because fewer than 5 percent of American adults today achieve the recommended level of physical activity in a week according to the current physical activity guidelines. Knowing that even short bouts of ‘brisk’ activity can add up to a positive effect is an encouraging message for promoting better health.”

Current physical activity recommendations urge Americans to get at least 150 minutes of moderate-to-vigorous physical activity (MVPA) a week, which can be accumulated in eight- to 10-minute periods. MVPA is defined as greater than 2,020 counts per minute measured with a tool called an accelerometer. This translates roughly to a walking speed of about 3 mph. But taking the stairs, parking at the far end of the lot, and walking to the store or between errands are choices that can add up and can make a positive health difference, the researchers note.

The study also showed that higher-intensity activity was associated with a lower risk of obesity, whether in “bouts” of fewer or greater than 10 minutes. This may be especially important news for women, who are, on average, less physically active than men. However, neither the men nor the women in this study came close to the weekly 150-minute recommendation with bouts of eight- to 10-minutes. However, when adding shorter bouts of higher-intensity activity, men exceeded the recommendation on average, accumulating 246 minutes per week, and women came much closer to meeting it, at 144 minutes per week on average.

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