Growth Spurts May Wipe Out Adolescent Obesity

A new model of childhood weight gain suggests that obese children, particularly boys, may be able to outgrow the condition.

Researchers at the US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK; Bethesda, MD, USA) developed a mathematical model of childhood energy balance that accounts for healthy growth and development of obesity, and that makes quantitative predictions about weight-management interventions. The model was calibrated to reference body composition data in healthy children, and validated by comparing model predictions with data other than those used to build the model.

The model simulated growth through a gradual increase in energy intake from ages 5 to 18 of 1,200 kcal per day in boys, and 900 kcal per day in girls, with adjustments for halted growth in early adulthood and a higher resting metabolic rate (compared with adults). Excess weight gain and obesity were not clearly defined in the model, due to the variability of healthy growth in children as well as the trajectories of excess weight gain. Obesity was simulated by gradually increasing the rate of energy intake and concomitantly increasing energy expenditure by 300 kcal per day.

The model showed that at ages 5 to 11, when compared to healthy children at 10-years-old, the mean energy intake was about 750 kcal per day higher in obese boys versus healthy weight boys, and roughly 850 kcal per day higher in obese than in healthy weight girls. At the end of the simulated 6-year period, the obese boys and girls were predicted to eat an added 1,100 kcal per day and 1,300 kcal per day, respectively, compared with their healthy weight counterparts.

The authors also modeled a child "outgrowing" obesity through a simulation of decreased energy intake. This decrease was held from ages 11 to 16, and accounted for the rapid growth during those years. Boys in the simulation had a body composition that was almost normalized relative to healthy weight, implying that fat-free mass increased substantially, with concomitant loss of fat mass. Obese girls in the simulation, however, lost less fat over the same period, under the same parameters as obese boys. The study was published online in the Lancet Diabetes Endocrinology.

“A comparison of body weight between children in two time periods showed that body weight across all ages increased by an average 6.1 kg in boys and 5.7 kg in girls,” concluded lead author Kevin Hall, PhD, of the and colleagues. “Reducing energy intake in a cohort of children by a mean of around 200 kcal compared with that in 2003 to 2006 data will return the mean body weight to levels characteristic of the late 1970s, before the onset of the obesity epidemic.”

Related Links:
US National Institute of Diabetes and Digestive and Kidney Diseases