To read the full abstract: N Engl J Med. 2018;379(14):13031312.
This analysis of longitudinal BMI data from early childhood to adolescents in 51,505 German subjects (CrescNet patient registry) allows a new insight into BMI development, specific dynamics and BMI trajectories from childhood to early adulthood.
The exact pattern and time course of weight gain during childhood that leads to obesity is unclear. These authors tracked BMI values, obtained by measured height and weight data in individual children from infancy to adolescence in a large population (CrescNet patient registry | Germany) recruited from resident doctors, to determine the age at which children are most vulnerable to excessive weight gain that results in obesity in adolescence. They included in the analysis children who had at least one visit with a resident pediatrician between 0 and 14.9 years of age (childhood) and another visit between 15.0 and 18.9 years (adolescence) (n=51,505 subjects; 336,227 data points).
They found that: (a) the majority of normal BMI adolescents had normal BMI as children; (b) the majority of overweight adolescents had normal BMI for the first 4 years life and the percentage of overweight increased from age 5 years onwards; and (c) the majority of adolescents who were obese had normal BMI as infants, and became overweight or obese by age 5 years.
Among children who were obese at 3 years of age, the probability of being overweight or obese in adolescents was almost 90%. The comparison of changes in BMI-standard-deviation score (BMI-SD) from birth onwards showed that the BMI-SD-score was much more stable among adolescents in the normal BMI group than in the overweight/obese group. For overweight/obese adolescents, the greatest BMI acceleration occurred between 2 and 6 years of age.
The strengths of this study include the population-based design, the inclusion of 51,000 children and of 300,000 measurements (weight/height). This study impressively shows that early childhood is the critical age for the development of obesity and that there are specific dynamics and patterns of BMI in this early childhood period. In daily practice, this means that BMI acceleration rather than the absolute BMI alone appears to be important in identifying children at risk for obesity in later life.
From an evolutionary point of view the genomes of hunter-gatherers were adapted to low insulin sensitivity with a lifestyle comprising intense physical activity and a high-protein and low-carbohydrate diet (1). Individuals with a still preserved hunter-gatherers genome who become obese at age 48 years may need a low-carbohydrate (CHO) diet in order to prevent excessive weight gain. By contrast individuals with a so-called farmer genome, which adapted to a CHO-rich diet, who become obese in infancy might profit more from a low-calorie diet. The present data may help to differentiate these two groups of individuals and to stimulate further genomic and metabolic investigations.
Reference: 1. Hochberg Z. An evolutionary perspective on the obesity epidemic. Trends Endocrinol Metab. 2018; 29(12): 819826.