The role of breastmilk in body composition

We know that childhood obesity, rates of which are on the rise globally, predisposes us to obesity later in life. This, in turn, increases our risk of cardiovascular and metabolic disorders, but is there a silver bullet that can mitigate against this in the form of breastfeeding?

Prof Donna Geddes from the Faculty of Science at the University of Western Australia was one of the speakers at a recent international breastfeeding and lactation symposium hosted by Medela in London last month. Her paper was entitled ‘How fat is too fat? Development of body composition over the first year of life in breastfed infants’.  

“The incredible thing about breastfeeding is that, despite our diets nowadays, the meta-analyses still show a 10-20% lowering of risk of obesity if you have been breastfed,” she said. 

“More and more benefits of being breastfed are being documented in the literature. The diseases for which risk factors are reduced in children that are breastfed include cancers such as childhood leukaemia and lymphoma, non-alcoholic fatty liver disease and endometrial cancer, as well as non-communicable diseases such as cardiovascular disease and type 1 and 2 diabetes. The mechanisms by which these protective benefits are conferred to the baby are still elusive because of their complexity.” 

The study of animal models has provided support for the idea that nutrition provided to babies very early in life impacts both obesity and metabolic programming and subsequently disease risk later in life, explained Prof Geddes. 

“Constant signalling occurs between the mother and foetus during pregnancy which affects foetal growth and development. Breastmilk may be perceived as an extension of maternal signalling, modulating growth, development and programming in the first two years of life,” she said.

Prof Geddes said that while breastfed babies grow rapidly in the first six months they then slow down in the next six months, “so that period of exclusive breastfeeding is very different to formula feeding, and it is thought to be protective”.

“However, we have this hypothesis in the literature that rapid weight gain is bad. That it’s linked to obesity later on in life. But are breastfed children programmed to have better outcomes? So is it growth, or is it modulation of body composition? 

“We have a severe lack of understanding of how that body composition develops through the first year of life,” she added.

Donna Geddes presenting at the symposium(click to enlarge)

Prof Geddes and her team set out to run a longitudinal cohort study of lactation. They recruited mothers and babies and took a series of measurements over a year. 

“We measured the baby’s body composition and growth and we measured the mother’s body composition and milk production, which we then tracked throughout the first 12 months. We looked at gastric emptying, which is involved in appetite regulation because we know breastfed children regulate their appetite really well.”

The data this study generated suggests that intervening in any way when a breastfed baby is considered to be ‘too fat’ can do more harm than good. While they grow faster, their milk intake does not actually increase over the first six months and then starts to decrease.

“For breastfed babies, there was no correlation between dose and weight gain. The dose of human milk components modulates the infant’s body composition over 12 months,” she explained.

The study also looked at the components in the milk as being more than just food for the baby. Taking 24-hour milk production and intake, they established the 24-hour ‘dose’ of each component and they found that several of the component doses related to the adiposity and the lean mass of the baby, for example leptin.

“The mother was modulating, through the dose of leptin, how the baby’s body composition was being developed. 

“Leptin levels in milk are related to the mother’s adiposity. We found the same scenario with casein, where an increased dose of casein was related to higher infant adiposity and lower lean tissue accretion.

“Part of the puzzle of how milk affects infant body composition development also lies in breastfeeding patterns and the volume of milk consumed by the baby. Typically, we found if the baby fed more frequently they received more milk over 24 hours, and therefore higher doses of milk components, which were linked to increased infant adiposity. The feeding frequency or milk volume was not however, associated with the mother’s adiposity, explained Prof Geddes.

In terms of modulating breastmilk, according to Prof Geddes we now have a window of intervention where perhaps we can encourage mothers to change their body composition, pre-pregnancy ideally, that will affect the amount of leptin in their milk to hopefully achieve better outcomes for the baby. 

This area is now the subject of further study by her research team at the University of Western Australia.