In Childhood, Heaviness leads to Inactivity, But Not the Other way Around

A new study suggests that physical inactivity in children is the result of obesity, not the cause of it, and is linked to early feeding habits, challenging the popular view that getting overweight children to exercise more is the key to preventing childhood obesity.

Researchers at Peninsula Medical School (PMS, Plymouth, United Kingdom) conducted a nonintervention prospective cohort study involving 202 children (53% boys, 25% of which were overweight or obese) whom were recruited from 40 Plymouth primary schools as part of the EarlyBird study, which examines children annually from 7 to 10 years. The main outcome measures were physical activity (PA), as measured using accelerometers worn for one week at each annual time point. The researchers then analyzed the total volume of PA and the time spent at moderate and vigorous intensities. The children's body fat percentage (BF%) was measured annually by dual energy X-ray absorptiometry.

The results showed that BF% was predictive of changes in PA over the first three years, but PA levels were not predictive of subsequent changes in BF% over the same follow-up period. While a 10% higher BF% at age 7 years predicted a relative decrease in daily moderate and vigorous intensities of 4 minutes from age 7-10 years, more PA at 7 years did not predict a correlated relative decrease in BF%. The researchers thus concluded that physical activity had no effect on weight change, but weight change did lead to less physical activity. The researchers suggested that children who become overweight may lack confidence and feel embarrassed about how they look, and this stops them taking part in sporting activity and exercise. The study was published early online on June 23, 2010, in Archives of Disease in Childhood.

"The implications of this study are very important for public health policy, because it implies that the physical activity of children, which is vital for their fitness and general wellbeing, may never improve unless childhood obesity is tackled first,” said lead author Terry Wilkin, M.D., a professor of endocrinology and metabolism at PMS. "Calorie reduction, rather than physical activity, appears to the key to weight reduction in overweight and obese children, pointing to early feeding errors, and the contribution of portion size, calorie-dense snacks, and sugary drinks.”

Other findings from the EarlyBird study show that the children's inactivity is not due to lack of green spaces and sport centers, and that social inequality is no longer a major factor, as all children are at risk. Many parents of obese children are obese themselves, and seem unaware and unconcerned of their condition. The researchers therefore suggest that it may be more effective to target the obese parent than the obese child. They also found that healthy weight for life starts at birth, and therefore that parents do not overfeed low birth weight babies, as they are most at risk of later weight gain.

Related Links:
Peninsula Medical School
EarlyBird Study