The facts and fictions of baby fat have been revealed in the first-ever study of Aotearoa New Zealand new-borns body composition, including a surprise that could refocus early healthcare.
Researchers in the Liggins Institute-led study used a special air displacement machine combined with tape-measurements and sensitive scales to determine the fat mass and fat-free mass (everything else) of 440 babies born in Auckland between May 2015 and April 2018.
Babies were classified as either Maori and Pacific, European or Asian.
Maori, Pacific, Asian comparisons
Researchers found that, on average (a) Maori and Pacific babies were bigger (longer, larger head circumference) than European and Asian babies at birth, and heavier than Asian babies – all well-established facts – but the revelation was that they were also leaner: the extra weight came from fat-free mass (bones, muscles, organs), not fat mass.
Asian babies were the lightest, shortest and smallest, but had similar amounts of fat mass to babies of other ethnicities, and therefore the highest percentage of fat mass.
Boy babies were heavier, longer and had larger heads than girl babies, but they were also leaner, with a lower percentage of fat mass – a pattern long-recognised in childhood and adulthood.
Study Lead Tanith Alexander, is a PhD student at the University-based Liggins Institute and dietitian at Kidz First, Middlemore Hospital.
She said, “We wanted to see if knowing body composition at birth could help identify risk factors for later metabolic disease, such as obesity and Type 2 Diabetes, and interventions for long-term health. The finding that Maori and Pacific babies were heavier but leaner was somewhat surprising, because by the time they reach childhood, they experience the highest rates of overweight and obesity of all ethnicities. This suggests that environmental factors in our society are mostly driving this shift in body composition.”
While fat mass percentages differed by ethnicity and sex, the absolute amount of fat mass was similar across all babies in the study.
“This raises the possibility of a ‘target’ mass of fat for new-born babies to aid transition to life outside the womb. New-borns need a certain amount of fat to maintain their body temperature and for energy stores until breastfeeding fully kicks in,” says Ms Alexander said.
The ‘thin-fat’ types
“Although our findings suggest that Asians are born with the ‘thin-fat’ body type, this underlines that small or thin babies do not need fattening up to make them the same size as other babies, as they all have the same fat stores. In fact, rapid weight-gain during the first few years of life has been linked to childhood obesity, which in turn raises your risk of developing health problems in adulthood such as obesity, type 2 diabetes and cardiovascular disease.”
The researchers say that the findings once again highlight the importance of health promotion from the earliest years to set children up for life-long health. Actions could include supporting mothers to breastfeed, guidance around introduction of solids, community-based promotion of healthy eating and exercise for children and whānau, and regulatory or pricing changes to make healthy food cheaper and more accessible.
The study was published in the journal Early Human Development in January 2020 and funded by Counties Manukau Health and The Nurture Foundation for Reproductive Research. The other researchers are from Massey University and Boston University.
Source: Liggins Institute, University of Auckland