Tracking of overweight and obesity from early childhood to adolescence

Identification of children at risk of adverse levels of adiposity is possible before preschool age. However, most important are general preventive efforts for all children through adolescence.

Background: High prevalence of childhood overweight/obesity is a serious health concern due to related immediate and long-term health problems. Early identification of children at risk is therefore of importance, as preventing or delaying the onset of obesity may influence future health. Higher prevalence rates of overweight/obesity in children from Northern-Norway compared to the rest of the country, have been reported. The aim of this study was to explore how childhood body mass index (BMI) and growth were related to body composition measures in adolescence.

Methods: We used data from 961 adolescents (48% girls) participating in the population-based cohort study Fit Futures (FF) conducted in 2010-2011 and 2012-2013 in Tromsø, Norway. Anthropometric data were retrospectively obtained from childhood health records at 2.5 and 6.0 years of age. Anthropometric measures as well as body composition measured by dual X-ray absorptiometry, was obtained in FF at 16 and 18 years of age. In tracking analyzes normal weight or overweight/obesity (adult BMI ≥25 kg/m2), based on BMI and according to international age- and sex-specific cut-off values, at adolescence was the outcome. In addition, we assessed associations between childhood BMI, growth (BMI gain) with fat mass index (FMI, kg/m2), fat-free mass index (FFMI, kg/m2) standard deviation scores (SDS) at 16-18 years as outcomes.

Results: At 18 years of age 21% of girls and 28% of boys were overweight/obese. The degree of tracking of BMI from 2.5 and 6 years of age up to 16-18 years of age was moderate to strong. Children with severe overweight/obesity (adult BMI ≥27 kg/m2) had considerably higher odds of later overweight/obesity compared to their normal weight peers, with an OR of 3.01 (95% confidence Interval: 1.47 to 6.18) and an OR of 11.51 (6.63 to 19.99) at ages 2.5 and 6, respectively. Overweight/obesity at 6 years of age as well as greater BMI gain were strong predictors of higher FMI in adolescence. Conditional BMI gain was associated with higher FMI and FFMI with the strongest associations seen between age 6-16 years: FMI SDS: β= 0.67, (95% confidence Interval: 0.63, 0.71), FFMI SDS: 0.46 (0.39, 0.52), FMI SDS: 0.80 (0.75, 0.86), FFMI SDS: 0.49 (0.43, 0.55) in girls and boys, respectively.

Conclusions: The degree of tracking of BMI from childhood to adolescence was moderate to strong. Severe overweight/obesity at 2.5 and 6 years of age was a strong predictor of later overweight/obesity. Greater BMI gain between 6.0 and 16 years of age were most strongly linked to adiposity in adolescence. Early identification of children at risk of adverse levels of adiposity is possible. However, preventive efforts should focus on a healthy weight development for all, both in early childhood and adolescence.