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Postnatal growth may identify infants genetically predisposed to obesity
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Genetic obesity susceptibility appears to be associated with postnatal gains in infant weight and growth, according to a review of medical literature published in JAMA Pediatrics.
“We found that genetic factors that predict adult obesity were associated with faster weight gain and growth during infancy,” Ken K. Ong, FRCPCH, of the University of Cambridge, England, told Endocrine Today. “The findings indicate that the biological mechanisms that predispose people to later obesity are already active from birth.”
Ong, along with Cathy E. Elks, PhD, also of the University of Cambridge, and colleagues from other institutions conducted a meta-analysis that included 3,031 children from four cohort studies in England, France and Spain to test associations between genetic obesity susceptibility and body size or composition at birth through age 5 years.
Genetic obesity susceptibility was represented by a combined obesity risk-allele score calculated in each child as the entirety of 16 different alleles associated with higher adult BMI. Main outcomes were age- and sex-adjusted standard deviation scores (SDS) for weight, length/height, BMI, fat mass, lean mass and percentage of body fat at birth and age 1 year, 2 to 3 years and 4 to 5 years.
The obesity risk-allele score did not demonstrate an association with infant size at birth. However, at age 1 year, the risk-allele score was positively associated with weight (beta=0.02 SDS per allele; P=.009) and length (beta=0.02 SDS per allele; P=.01) but not with BMI (beta=0.013 SDS per allele; P=.11).
At age 2 to 3 years, associations were stronger for weight (beta=0.033 SDS per allele; P<.001) and height (beta=0.025 SDS per allele; P<.001) and also for BMI (beta=0.024 SDS per allele; P=.003).
“Surprisingly, in infants, these genetic factors promoted proportionate gains in both fat and lean (muscle) mass,” Ong said. “This indicates that the mechanisms of these genes very likely involve greater appetite and food intake rather than specific effects on body fat.”
The obesity risk-allele score showed positive associations with postnatal fat mass at age 1 year (beta=0.032 SDS per allele; P=.05), 2 to 3 years (beta=0.049 SDS per allele; P=.006) and 4 to 5 years (beta=0.028 SDS per allele; P=.009).
Positive associations also were seen for postnatal lean mass at age 1 year (beta=0.038 SDS per allele; P=.008), 2 to 3 years (beta=0.064 SDS per allele; P<.001) and 4 to 5 years (beta=0.047 SDS per allele; P<.001); however, this was not so for body fat percentage (P>.15 at all ages).
“Our findings contribute to the growing evidence that lifelong obesity risk can be predicted at very young ages, and hopefully modified by very early changes in lifestyle and diet,” Ong said. – by Allegra Tiver
For more information:
Ong can be reached at Medical Research Council Epidemiology Unit, University of Cambridge, Addenbrooke’s Hospital, Box 285, Cambridge CB2 0QQ, England; email: ken.ong@mrc-epid.cam.ac.uk.
Disclosure: The researchers report no relevent financial disclosures.
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