Brief Walks Offset Metabolic Risk From Prolonged Sitting in Kids

Nicola M. Parry, DVM

August 28, 2015

For children who engage in long periods of sitting, taking short walking breaks can reduce their blood glucose, insulin, and free fatty acid levels without increasing subsequent total energy intake, a new trial suggests.

Britni R. Belcher, PhD, MPH, a cancer prevention fellow at the National Institutes of Health's National Cancer Institute and assistant professor of preventive medicine at the University of Southern California, and colleagues published the results of the randomized crossover study online August 27 in the Journal of Clinical Endocrinology and Metabolism.

"Sustained sedentary behavior after a meal diminishes the muscles' ability to help clear sugar from the bloodstream," Dr Belcher explained in a news 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."

According to National Health and Nutrition Examination Survey data, children spend about 6 hours per day engaged in sedentary activities. Sedentary behaviors, such as television watching, are also associated with reduced fruit and vegetable intake, and increased fast food and snack consumption. In addition, studies have linked prolonged sedentary behaviors in children with pediatric obesity and metabolic health problems. However, although recent studies have investigated the acute metabolic effects of interrupting sitting as a potential prevention strategy in adolescents and young adults, findings have been mixed.

Therefore, Dr Belcher and colleagues aimed to examine the effects of continuous vs interrupted sitting on metabolism and energy intake in children and included 28 healthy and normal-weight 7- to 11-year-olds in their study. The researchers excluded overweight or obese children, as well as those with impaired glucose tolerance, type 2 diabetes, or other endocrine disorders that could lead to obesity.

They randomly assigned the children to engage in 3 hours of either continuous sitting or sitting interrupted by walking (a 3-minute, moderate-intensity walk on a treadmill every 30 minutes). On a separate day, both groups switched to engage in the alternate regimen.

Children in the interrupted sitting group had a 32% lower insulin area under the curve (AUC; P < .001), 17% lower C-peptide AUC (P < .001), and 7% lower glucose AUC (P = .018) than those in the continuous sitting group. They also had significantly lower insulin (P = .036) and free fatty acid (P = .009) concentrations. Moreover, the exercise did not affect children's appetites. When provided with a lunchtime buffet meal, children's total energy intake did not significantly differ, regardless of whether they had engaged in continuous or interrupted sitting that day (P = .85).

"This study, to the best of our knowledge, provides the first evidence that interrupting sitting time with brief bouts of moderate-intensity walking can improve short-term metabolic function in healthy non-overweight children," the authors write.

"Should these findings be confirmed and extended in longer-term studies, interrupting sitting may be an effective prevention strategy to reduce cardiometabolic risk in children."

This study was supported by the Intramural Research Programs of the National Cancer Institute and National Institute of Child Health and Human Development. Dr Belcher was supported by a postdoctoral training award from the National Cancer Institute's Cancer Prevention Fellowship Program in the Division of Cancer Prevention. Coauthors received support from the National Cancer Institute's Division of Cancer Control and Population Sciences, Intramural Research Program of the National Institutes of Health, and the National Institutes of Health Office of the Director. The authors have disclosed no relevant financial relationships.

J Clin Endocrinol Metab. Published online August 27, 2015. Full text

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