Insulin Dynamics in Preteens

Adiposity plays a determining role in cardiometabolic health even in pre-teens, according to a new study that found increased body fat at ages 8 to 10 predicted increased insulin sensitivity and secretion two years later.

The results also suggest that increased physical activity and reduced screen time would help improve insulin dynamics.

A healthy lifestyle plays a critical role in preventing or delaying the onset of type 2 diabetes mellitus (T2DM) in adults, but little is known about the impact of lifestyle habits on the risk of T2DM in children.

These researchers, led by Mélanie Henderson, MD, PhD, division of endocrinology, Centre Hospitalier Universitaire Sainte-Justine in Montreal, Quebec, conducted a prospective longitudinal cohort study of 630 children who had at least 1 obese parent. The goal of the study was to assess whether adiposity, fitness, moderate-to-vigorous physical activity, and screen time predict insulin sensitivity or insulin secretion during a two-year period.

The participants from the Quebec Adipose and Lifestyle Investigation in Youth cohort were assessed at baseline (ages 8-10 years) and two years later. Fitness was measured by peak oxygen consumption, percentage of body fat (adiposity) by dual-energy x-ray absorptiometry, moderate-to-vigorous physical activity using accelerometry, and screen time by average daily hours of self-reported television, video game, or computer use.

Insulin sensitivity was measured by the homeostatic model assessment of insulin resistance and an oral glucose tolerance test-based index. Insulin secretion was measured using the area under the curve of insulin to glucose during the first 30 minutes of the oral glucose tolerance test and using the area under the curve of insulin to glucose over two hours.

At baseline, slightly more than half (56.2%) of the children were of normal weight, 19.2% were overweight, and 22.7% were obese.

On average, they did 47.7 minutes per day of moderate-to-vigorous physical activity, had 2.2 hours per day of screen time, and their median percentage of body fat was 25.3%.

At the two-year follow-up, 564 children were evaluated.

Adiposity and changes in adiposity were the central predictors of insulin dynamics over time. Every additional 1% of body fat at ages 8 to 10 years decreased insulin sensitivity by 2.9% and led to a 0.5% increased requirement in the area under the curve of insulin to glucose during the first 30 minutes of the oral glucose tolerance test two years later.

“Higher levels of moderate-to-vigorous physical activity and lower screen time appear to be beneficial to insulin sensitivity in part through their effect on adiposity levels,” the researchers stated.

Every additional 10 minutes per day of physical activity at baseline was associated with a 3.5% lower body fat at follow-up, even after taking into account fitness and screen time. Every one-hour increase in screen time at baseline predicted a 2.9% increase in body fat at follow-up, even after taking into account physical activity and fitness.

“Public-health strategies that promote a healthy body weight through lifestyle habits and likely lower energy intake need to target children early," they stated.

Reference: Henderson M, et al. Influence of adiposity, physical activity, fitness, and screen time on insulin dynamics over 2 years in children. JAMA Pediatr. 2016 Feb 8. [Epub ahead of print]