Breast proves best for reducing young flab

The longer infants are breastfed, the lower their chance of becoming overweight adolescents, a new study suggests.

The findings, published in Epidemiology, add to the not-always-consistent body of research on breastfeeding and childhood weight gain.

Several studies have suggested breastfed babies are less likely to become overweight than bottle-fed infants, but others have found no such benefit or that the weight difference does not last long.

But in the latest study, Harvard researchers found that even within a single family children who were breastfed for a longer time were slightly less likely to become overweight than their siblings who were breastfed for a shorter period.

The difference within families was similar to that found in the study population as a whole, where each four-month increase in breastfeeding was linked to a 6 per cent dip in the risk of being overweight by adolescence.

Since siblings are raised under much the same circumstances, the findings "lend credence" to the idea that breastfeeding itself confers a weight benefit, says Dr Matthew Gillman, the study's lead author.

One of the pitfalls in studying the effects of breastfeeding on childhood weight is that both are "socially patterned", says Dr Gillman, an associate professor of nutrition at the Boston's Harvard School of Public Health.

For example, mothers with more education or higher incomes are more likely to breastfeed, and their children are also less likely to be overweight. So studies need to control for such influences.

Following families in which siblings had different breastfeeding patterns accomplished that to a large degree.

Dr Gillman and his colleagues surveyed 5614 siblings between the ages of 9 and 14 who had been part of a larger study that had previously linked longer breastfeeding duration to a lower risk of obesity later in life.

The fact that the findings within families were close to those in the overall group suggests that breastfeeding itself affected weight later in life, according to the researchers.

The reason was not entirely clear, but one general theory, Dr Gillman says, is that breast milk has lasting metabolic effects that aid in weight control. Another is that breastfeeding has behavioural effects; with breastfeeding, the length of any one feeding depends mostly on the baby, whereas mothers who bottle-feed might keep feeding their infants until the bottle is empty.

Dr Gillman says breastfeeding might encourage more "self-regulation" of calorie intake later in life.

Whatever its effects on weight, he says, breast milk is considered the best nutrition for infants, so the possibility of weight benefits could be seen as a potential bonus to a healthy practice.

- REUTERS