At least 20% of adult obesity is caused by over-feeding in infancy, according to Professor Atul Singhal from the MRC Childhood Nutrition Research Centre at the Institute of Child Health in London.
While breastfed babies limit their own intake of milk because they have to work hard to get it, bottle-fed babies lie back and swallow what they are given. The danger, according to Singhal, is that they will be offered more than they need, building up an appetite for the future.
“When they are exposed to high-protein, high-fat foods, they are more likely to become obese,” he said.
The message to parents and to health professionals is that – as long as a baby is healthy and born at full-term – a small infant should not be given extra food. Those who are at the bottom end of the growth chart should stay there, he says. Plump and bouncing babies are not necessarily the ideal.
Singhal is lead author on a study published today in the American Journal of Clinical Nutrition, which has established scientifically for the first time something that has been observed in animals and humans before – that over-nutrition in early life leads to being overweight and associated problems in later life.
Singhal and colleagues followed up children who were involved in two studies from the 1990s when they were newborn babies. Some were given nutritionally enriched babymilk – now only ever given to weak, premature babies – and others were given standard formula.
Those who were given the extra nutrition had a fat mass by the age of five to eight that was 22% to 38% greater than those who were fed standard formula. Increased fat in childhood is a known risk for being overweight in adulthood.
“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,” said Singhal.
But the implications of the study go beyond the use of enriched formula milk, to the over-feeding of any baby. “In public-health terms, it supports the case in the general population for breastfeeding – as it is harder to overfeed a breastfed baby,” Singhal said.
He pointed out that formula milk is based on cow’s milk – and that cows gain weight much faster than humans.
Not every woman can or wants to breastfeed, but Singhal hopes that this study and other work his team have been doing for the last 10 years will persuade parents and professionals that babies do not need feeding up. As long as the baby is healthy, he said, nobody should worry about his or her weight.
He did not want mothers to feel guilty about having a fat baby, he said, but they and healthcare professionals “need to recognise that there is such a thing as an overfed baby”.