The study sheds light on a potential way to reconfigure the school day to create opportunities for physical activity. More work would be needed, researchers say.
Small periods of physical activity can go a long way to help a child’s health, according to a new study by researchers at the National Institutes of Health (NIH) and published online in the Journal of Clinical Endocrinology and Metabolism.
Brief periods of exercise may offset what would otherwise be sedentary periods, and are preferable to no exercise at all, the researchers found. Children who interrupted periods of sitting by walking 3 minutes at moderate intensity every 30 minutes had lower levels of blood glucose and insulin, compared with periods when they remained seated without a break for 3 hours.
Areas of NIH taking part in the study included the National Cancer Institute, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the National Heart, Lung, and Blood Institute, and the National Institute of Diabetes and Digestive and Kidney Diseases, according to a statement from NIH.
The study offers a potential alternative to the way the school day is configured as a way to combat childhood obesity, which puts young people at risk of developing type 2 diabetes mellitus, cancer, and cardiovascular disease. US children spend about 6 hours a day not moving—either sitting or reclining—and these behaviors are linked to rising rates of obesity and insulin resistance. According to the CDC, more than one-third of children and adolescents are overweight or obese.
Walking a mile in 15 to 20 minutes can lower glucose and insulin levels, but this study showed that as an alternative, interrupting the day with quick doses of activity could have positive health effects.
To conduct the study, researchers enrolled 29 healthy children of normal weight, who came to the NIH center in Bethesda, Maryland, for 2 experimental visits each. Children were assigned at random to 1 of 2 groups. In the first group, children either watched television or read or 3 hours. In the other group, the children alternated between sitting and walking on a treadmill every 30 minutes for 3 minutes, which increased their heart rate.
Each child returned to the NIH site within 7 to 30 days to spend 3 hours doing the opposite activity from the prior visit: the treadmill group took in the sedentary activity, and the sedentary group completed the treadmill activity.
After each session, the children took an oral glucose tolerance test, which required them to drink “glucola,” which resembles soda and contains sugar glucose. Participants received a blood test to see how well they absorbed the glucose and how much insulin they produced. On walking days, the children had blood glucose levels that were 7% lower on average than on the day they spent 3 hours sitting. Insulin levels were 32% lower, and blood levels of free fatty acids, which are a sign of T2DM, were also lower on walking days. So was C peptide, an indicator of how well the pancreas is controlling blood sugar.
“We know that 30 minutes of more of moderate physical activity benefits children’s health<’ said senior author Jack A. Yanovski, MD, chief of NICHD Section on Growth and Obesity. “It can be difficult to fit longer stretches of physical activity into the day. Our study indicates that even small activity breaks could have a substantial impact on children’s long-term health.”
He said more work would be needed to determine if such breaks could be incorporated into the school day as an effective way to combat obesity and related illnesses.
Several reasons have been offered why children are less likely to have sustained periods of exercise compared with 20 years ago. These include the increased popularity of video games, fear of crime in urban neighborhoods, and the unwillingness of parents to allow children to walk to school for safety reasons.
Belcher BR, Berrigan D, Papachrisotopoulou A, et al. Effects of interrupting children’s sedentary behaviors with activity on metabolic function: a randomized trial [published online August 27, 2015]. J Clin Endocrinol Metab. 2015; DOI: http://dx.doi.org/10.1210/jc.2015-2803.