Nutrition in infancy and long-term risk of obesity: evidence from 2 randomized controlled trials

Growth acceleration as a consequence of relative overnutrition in infancy has been suggested to increase the risk of later obesity. However, few studies have investigated this association by using an experimental study design.

We investigated the effect of early growth promotion on later body composition in 2 studies of infants born small for gestational age (weight <10th percentile in study 1 and <20th percentile in study 2).

We reviewed a subset of children (n = 153 of 299 in study 1 and 90 of 246 in study 2) randomly assigned at birth to receive either a control formula or a nutrient-enriched formula (which contained 28-43% more protein and 6-12% more energy than the control formula) at 5-8 y of age. Fat mass was measured by using bioelectric impedance analysis in study 1 and deuterium dilution in study 2.

Fat mass was lower in children assigned to receive the control formula than in children assigned to receive the nutrient-enriched formula in both trials [mean (95% CI) difference for fat mass after adjustment for sex: study 1: -38% (-67%, -10%), P = 0.009; study 2: -18% (-36%, -0.3%), P = 0.04]. In nonrandomized analyses, faster weight gain in infancy was associated with greater fat mass in childhood.

In 2 prospective randomized trials, we showed that a nutrient-enriched diet in infancy increased fat mass later in childhood. These experimental data support a causal link between faster early weight gain and a later risk of obesity, have important implications for the management of infants born small for gestational age, and suggest that the primary prevention of obesity could begin in infancy.