Breastfed babies may become lean teens

The Australian

January 11, 2006 - 7:49AM

A new study suggests that the longer infants are breastfed, the lower 
the likelihood they'll be overweight as adolescents, a relationship 
that does not appear to be influenced by sociocultural factors.

The findings, published in the journal Epidemiology, add to the not 
always consistent body of research on breastfeeding and childhood 
weight gain. While a number of studies have suggested that breastfed 
babies are less likely to become overweight than bottle-fed infants, 
others have found no such benefit or that the weight difference does 
not last far into childhood.

In the new study, however, 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 4-month increase in breastfeeding 
was linked to a 6 per cent dip in the risk of becoming 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, Dr Matthew W. Gillman, the study's lead 
author, told Reuters Health.

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

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 accomplishes that to a large degree.

For their study, Gillman and his colleagues surveyed 5,614 siblings 
between the ages of 9 and 14 who were 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 affects weight later 
in life, according to the researchers.

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

In this way, Gillman explained, breastfeeding may encourage more 
"self-regulation" of calorie intake later in life.

Whatever the effects of breastfeeding on a child's weight, he noted, 
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.

Experts recommend that babies be breastfeed exclusively for at least 
the first six months of life.

© 2006



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