Two studies have found that babies who put on weight too fast in their first months are more likely to become fat as adults. The studies showed that at 5–8 years old, children who were given the enriched formula had more body fat than those who were given normal formula. This suggests that faster weight gain as a baby causes children to gain a higher proportion of fat mass when they are older. This corroborates with earlier research that say “overfeeding” in infancy – in this case by using nutrient-enriched formula – increases the risk of obesity later in life. Scientists say that the risk is irrespective of gender, height in childhood or socioeconomic status.
The studies had their share of flaws. Both of the studies had a high rate of drop-outs that could have skewed the results. Also, the studies did not look at children who had normal birth weight. One of the studies did not look at Body Mass Index (BMI) - a standard measure of obesity. Instead it looked at the children’s fat mass. As the children were not followed up into adolescence and adulthood, it is incorrect to say that these children were “primed for a life of obesity”.
The study was carried out by researchers from University College London, University Hospital Nottingham, Leicester General Hospital, Royal Hospital for Sick Children in Glasgow, the Wishaw General Hospital, the Southern General Hospital in Glasgow and the Danone Research centre for Specialized Nutrition in the Netherlands. It was funded by the Medical Research Council (UK) and other organizations, with contributions from Farley’s Health Products and Nutricia Ltd. It appeared in the American Journal of Clinical Nutrition.
The results collated the findings of two randomized controlled trials. For the studies the teams included newborn babies as soon as possible after birth from 10 UK hospitals to take part in the two studies. First Study recruited babies between 1993 and 1995, and second study between 2003 and 2005. All the babies were born at full term (after 37 weeks) but were small for gestational age (SGA). The babies in study 1 were below the 10th percentile for their gestational age and those in study 2 were below the 20th percentile, according to UK growth charts. The mothers were given an option of feeding their baby as they wished.
Babies who were bottle fed were randomly assigned to receive either standard formula (the control group) or a nutrient-enriched formula (the intervention), with a higher protein and energy content designed to promote rapid growth. The formulas were given until the babies were nine months old in study 1 and until they were six months old in study 2. A total of 545 babies were originally enrolled in the two studies, and in study 1 a reference group of 175 breastfed babies was also recruited. In both studies, researchers estimated fat mass using callipers to measure skin fold thickness.
As results only 243 of the original 545 infants could be followed up. In both studies, fat mass in those who had been given normal formula was lower than in those given the enriched formula (after adjustment for sex) at 5–8 years of age. In the first study children who had been on normal formula had 38% less fat mass than those in the enriched formula group. In the second study children who had been on normal formula had 18% less fat mass than those in the enriched formula group. A further analysis suggested that in the group of breastfed babies, faster weight gain in infancy was also associated with greater fat mass later.
According to Professor Atul Singhal from the MRC Childhood Nutrition Research Centre at the Institute of Child Health in London at least 20% of adult obesity is caused by over-feeding in infancy. “When they are exposed to high-protein, high-fat foods, they are more likely to become obese,” he said as a message to parents and health professionals. Singhal is the lead author of the studies. “This study robustly demonstrates a link between early nutrition and having more fat in later life in humans – a finding suggested by previous studies and confirmed in many other animals. Our findings are strong, consistent, show a dose-response effect, and are biologically plausible,” he said. He explained that this study had wider implications. “In public-health terms, it supports the case in the general population for breastfeeding – as it is harder to over-feed a breastfed baby,” Singhal said.
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