A new study suggests that, in children, short exercise sessions during otherwise sedentary periods may offset the effects from the lack of more sustained exercise.
The study, published recently in the Journal of Clinical Endocrinology and Metabolism, suggests in a media release from the National Institutes of Health (NIH) that children who interrupted sedentary periods with 3 minutes of moderate-intensity walking every half hour had lower levels of blood glucose and insulin, compared to periods when they remained seated for 3 hours.
“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,” says the study’s senior author, Jack A. Yanovski, MD, chief of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)’s Section on Growth and Obesity, in the release.
“Sustained sedentary behavior after a meal diminishes the muscles’ ability to help clear sugar from the bloodstream,” explains the study’s first author, Britni Belcher, PhD, a Cancer Prevention Fellow in the NIH’s National Cancer Institute (NCI)’s Health Behavior Research Branch and currently an assistant professor at the University of Southern California, in the release.
“That forces the body to produce more insulin, which may increase the risk for beta cell dysfunction that can lead to the onset of type 2 diabetes. Our findings suggest even short activity breaks can help overcome these negative effects, at least in the short term,” she notes.
To conduct the study, the researchers randomly assigned 28 healthy, normal-weight children who visited the NIH Clinical Center in Bethesda, Md, to one of two groups. Children in the first group remained seated for 3 hours and either watched television, read, or engaged in other sedentary activities. Children in the second group alternated sitting with 3 minutes of moderate-intensity walking on a treadmill (enough to increase their heart rate) every 30 minutes for the 3-hour period, the release explains.
Each of the children returned to the NIH Clinical Center 7 to 30 days later. Those who had remained seated for the full 3 hours during the initial session were switched to the group that had alternated sitting with moderate walking. Similarly, those who earlier took part in the moderate walking group were switched to the sedentary group, the release continues.
For each session, the children took an oral glucose tolerance test that involved drinking “glucola,” a soda-like drink containing the sugar glucose. After consuming the drink, the children had their blood tested to see how rapidly their bodies absorbed the glucose and how much insulin they produce.
On the days they walked, the children had blood glucose levels that were, on average, 7% lower than on the day they spent all 3 hours sitting. Their insulin levels were also 32% lower. Similarly, blood levels of free fatty acids — high levels of which are linked to type 2 diabetes — were also lower, as were levels of C-peptide, an indicator of how hard the pancreas is working to control blood sugar, the release explains.
After the sessions, the children were allowed to choose their lunch from food items on a buffet table. Based on the nutrient content of each item, the researchers were able to calculate the calorie and nutrient content of what each child ate. The short, moderate-intensity walking sessions did not appear to stimulate the children to eat more than they ordinarily would, as the children consumed roughly the same amounts and kinds of foods after each of the sessions, according to the release.
The study authors conclude in the release that, if larger studies confirm their findings, interrupting periods of prolonged sitting with regular intervals of moderate-intensity walking might be an effective strategy for reducing children’s risk of diabetes and heart disease.
Yanovski adds in the release that future studies are needed to examine if working such breaks into school class time could be part of effective strategies to prevent obesity-related illnesses.
[Source: National Institutes of Health]