ILLNESSOPEDIA

Weight control: every minute of brisk exercise counts

Every minute of high intensity physical activity counts in the war against weight gain, according to a new study published this week. Researchers from the University of Utah found a brief bout of intense exercise that works the heart and lungs has the same effect on preventing weight gain as the current recommendation of 10 or more minutes at a time.

The current guideline for Americans recommends that adults should do at least 150 minutes of moderate to vigorus physical activity in bouts of 8 to 10 minutes each week.

Moderate to vigorous physical activity is defined as a minimum of 2,020 counts per minute measured on an activity device called an accelerometer. Someone walking briskly at 3 miles per hour would reach this level.

Study leader Jessie X. Fan, professor of family and consumer studies at Utah, says:

"What we learned is that for preventing weight gain, the intensity of the activity matters more than duration."

She explains the finding is important because less than 5% of adults in the US are reaching the recommended level of physical activity.

"Knowing that even short bouts of 'brisk' activity can add up to a positive effect is an encouraging message for promoting better health," Fan adds.

What the researchers found is that higher intensity activity was linked to a lower risk for obesity, even when the periods of brisk exercise were less than 10 minutes.

In other words, even taking the stairs, leaving your car at the far end of the parking lot and walking briskly to the store count towards making a positive health difference.

The team says this could be good news for women in particular, because they tend to be less active than men on average, although their study found neither group came close to reaching 150 minutes a week with bouts of 8 to 10 minutes.

But when they counted shorter periods of higher intensity exercise, they found men reached 246 minutes per week on average, which is quite a bit more than the recommendation, and women came very close, at 144 minutes per week.

So the message is, where brisk exercise is concerned, every minute counts for health.

Benefits of higher intensity exercise bursts

The study involved 2,202 women and 2,309 men who took part in NHANES, the National Health and Nutrition Examination Survey.

The team selected participants aged between 18 and 64, excluding certain groups, such as pregnant women and people unable to walk.

For a week between 2003 and 2006, the participants wore accelerometers to record their physical activity. The team reviewed these results against other health and demographic data collected as part of NHANES.

The physical activity results were ranked into four categories according to duration and intensity:

Long bouts of higher intensity exercise (over 10 minutes, more than 2,020 counts per minute or cpm on the accelerometer) Short bouts of higher intensity (under 10 minutes, more than 2,020 cpm) Long bouts of lower intensity (over 10 minutes, 760-2,020 cpm) Short bouts of lower intensity (under 10 minutes, 760-2,020 cpm).

The researchers compared the exercise results against body mass index (BMI), a standard measure of body fat based on height and weight that applies to adult men and women. A BMI between 18.5 and 24.9 is considered healthy weight, a BMI between 25 and 29.9 is overweight; and over 30 is obese.

Small bursts: an extra minute of high-intensity exercise daily lowers obesity risks by 5% for women and 2% for men.

The analysis showed that each extra daily minute of higher intensity exercise lowered the chances of being obese by 5% for the women and 2% for the men.

For women, each daily minute of higher intensity short bouts was tied to a reduction in BMI of 0.07. In other words, each daily minute of brisk exercise burned the calorie equivalent of 0.41 pounds.

So a woman of average height 5 ft, 5 in can expect to shed nearly half a pound by adding 1 minute of brisk exercise a day - all other things staying the same.

The results for men were similar.

According to the US Centers for Disease Control and Prevention (CDC) moderate intensity activity is where you are working hard enough to raise your heart rate and break a sweat. One way to tell is that you can talk - but not sing - the words to your favorite song.

Brisk walking, riding a bike on level ground, or pushing a lawn mower are good examples of moderate intensity activity.

Moving to vigorous intensity activity would involve swapping the brisk walking for jogging, for example, because that is defined as breathing hard and fast, so your heart rate goes up quite a bit more. At this level, you will not be able to say much without pausing for breath.

A study published earlier this year found simply wearing a pedometer got people moving more and sitting less.