For people who want to avoid packing on extra pounds, a new study suggests going above and beyond commonly cited exercise guidelines.
“Current recommendations of 150 minutes of moderate-intensity exercise or 60 minutes of vigorous exercise per week might not be sufficient to prevent long-term weight gain,” lead researcher Trine Moholdt said in an email. “More is needed.”
How much more remains an open question.
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Moholdt, from the KG Jebsen Center of Exercise in Medicine at the Norwegian University of Science and Technology in Trondheim, advocates as big a dose of exercise as possible to stave off chronic illnesses and maintain weight.
The Institute of Medicine, a nonprofit group that is the health arm of the U.S. National Academy of Sciences, suggests normal-weight adults spend an hour a day doing moderate-intensity physical activity.
But the U.S. Department of Health and Human Services sets a lower bar, recommending at least 150 minutes a week of moderate-intensity aerobic activity for general health, though in prior research that amount has failed to be sufficient for weight control.
The American College of Sports Medicine says at least 20 minutes of vigorous-intensity exercise three days per week can also fulfill exercise recommendations.
The guidelines were set as a goalpost for adults aiming to avoid chronic illness, not to maintain weight.
Moholdt and her team studied the weight and exercise patterns of more than 19,000 adults, assessing them three times over 22 years. During that time, women gained nearly 19 pounds, on average, and men almost 17 pounds.
Only those who exceeded the recommended weekly 150 minutes of moderate-intensity exercise or 60 minutes of vigorous activity were able to avoid significant weight gain over both the first and second half of the study period, according to findings published in the British Journal of Sports Medicine.
Even participants who reported getting more exercise than prescribed gained weight, the authors write, calling some weight gain throughout adult life “inevitable.”
“The study clearly shows we gain weight over time,” said Dr. I-Min Lee. “If we want to slow the gain in weight, we need to increase the physical activity.”
“People with the largest gains in weight were the least active. Those with the smallest gains were the most active,” she said. An epidemiologist from the Harvard School of Public Health in Boston, Lee was not involved in the current study but has done similar research.
In a 2010 study, she found that middle-aged women who averaged about an hour a day of moderate-intensity exercise successfully kept off excess weight.
She described moderate-intensity exercise as walking briskly enough to be able to continue a conversation but being unable to sing.
The National Weight Control Registry, which gathers information from people who have successfully lost at least 30 pounds and kept it off for a least one year, reports that 90 percent of its members exercise, on average for about one hour a day.
In the U.S., where health experts predict half of adults will be obese by 2030 unless lifestyle habits change, the Centers for Disease Control and Prevention estimates that less than 48 percent of adults exercise enough to improve their health.
In the current study, inactive women gained 12.5 pounds more than women who exercised in excess of U.S. guidelines, and inactive men gained nearly eight pounds more than their most active counterparts. The research did not take participants’ diets into consideration.
Lee and Moholdt both stressed that any exercise is better than none.
“Everything counts,” Moholdt said. In another study, people who reported doing just one sweaty exercise session a week lived longer than those who weren’t active at all, she said.
“For weight-gain prevention, however, it seems that more is required,” she said.
“If you’re heavy and you are physically active,” Lee said, “you still are better off compared to someone who is overweight and not physically active.”