medwireNews: Brief periods of moderate exercise can offset the adverse metabolic effects of long bouts of sitting in children, shows a randomised trial.

Just 3 minutes of moderate-intensity walking every 30 minutes of a 3-hour period that was otherwise sedentary resulted in significantly lower levels of insulin, C-peptide and glucose, report Britni Belcher (National Cancer Institute, Bethesda, Maryland, USA) and co-researchers.

The findings tally with previous research showing that interrupting sitting caused reductions in insulin and C-peptide in adults.

“Taken together, these findings suggest that interrupting sitting with short bouts of activity has an effect on acute glucose homeostasis”, the researchers write in The Journal of Clinical Endocrinology & Metabolism.

They note, however, that the 28 children (aged 7–11 years) who completed the study were within the normal weight range for their age, so the results may not apply to overweight and obese children.

The study participants undertook an oral glucose tolerance test, during which they either sat still for the entire 3 hours, or did 3 minutes of walking on a treadmill every 30 minutes at 80% of their individual ventilatory threshold. The children undertook the two conditions in a randomised order, with a gap of at least 7 days between the two.

Children’s average insulin levels were significantly lower during the interrupted than uninterrupted sitting, at all timepoints except baseline, with the average area under the curve (AUC) being 32% lower (5448 vs 8036 µU/mL per min).

C-peptide levels were lower between 30 and 180 minutes, with the AUC being a significant 17% reduced (774 vs 929 ng/mL per min), and the average glucose AUC was a significant 7% lower (18,855 vs 20,181 mg/mL per min).

Levels of free fatty acids and triglycerides did not significantly differ, on average, leading the researchers to suggest that a longer sedentary period might be necessary to affect these variables.

They note that the increased activity during the interrupted sitting condition did not cause children to eat more from the buffet meal that was offered at the end of the sitting period, indicating that the amount of exercise undertaken was not sufficient to prompt increased energy intake.

“If these effects can be demonstrated over longer time periods, the small increases in energy expenditure from interrupted sitting and improved metabolic responses may potentially lead to better energy balance and glucose homeostasis in healthy children”, concludes the team.

By Eleanor McDermid, Senior medwireNews Reporter

J Clin Endocrinol Metab 2015; Advance online publication

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