Being fed breast milk exclusively in the first five months of life significantly reduces the genetic risk of becoming obese later in life, and may be a key intervention to prevent weight gain among children with the highest genetic risk, a recent study has found.
The study, “Exclusive breastfeeding can attenuate body-mass-index increase among genetically susceptible children: A longitudinal study from the ALSPAC cohort,” was published in the journal PLOS Genetics.
“Our study shows that while our genes do influence our risk of developing obesity, this predisposition is not irreversible and can be beneficially modified by exclusive breastfeeding,” Laurent Briollais, senior investigator at the Lunenfeld-Tanenbaum Research Institute, in Canada, and the study’s senior author, said in a press release.
Due to the many benefits of breastfeeding to newborns and mothers, the World Health Organization (WHO) recommends that all children are exclusively breastfed up to six months of age, and to continue breastfeeding along with additional foods until age 2 and beyond.
An increasing amount of evidence suggests that exclusive breastfeeding can reduce the risk of being overweight, but whether such benefit still holds in children with a higher genetic risk remains unclear. Also unknown is if breastfeeding in early ages is enough to counteract the weight gain attributed to genetic factors.
To find out, LTRI researchers investigated a large collection of data from the Avon Longitudinal Study of Parents and Children (ALSPAC). This longitudinal study included pregnant women from Avon, U.K., who were expected to give birth between April 1991 and December 1992. The children have been followed from birth into adulthood.
The analysis included 5,266 children, comprising 2,690 boys and 2,576 girls, who had available data on the duration of exclusive breastfeeding — meaning that no other source of milk or solid food was consumed — and genetic material to estimate a genetic risk score (GRS).
GRS ranged from 0, or no genetic risk, to 10 (highest genetic risk), based on 94 variations in previously validated obesity genes.
Results showed that the effects of GRS on body mass index (BMI) increased with age, with significant differences becoming evident from age 5. In girls, an increase in 2.5 points in the GRS made them gain 0.39 kg/m2 in BMI at age 7, compared to girls with a lower GRS, and 0.75 kg/m2 more at age 18.
In boys, the same increase in GRS meant a 0.61 kg/m2 higher BMI at age 7 and a nearly 2-unit increase in BMI at age 18.
As a child develops, BMI increases rapidly during the first year of life, reaching an adiposity peak, and then decreases and reaches a lower point at age 6. BMI then increases again throughout childhood in a rise called adiposity rebound.
GRS had no impact on the age at which the adiposity peak occurred. Yet, higher risk scores made adiposity rebound happen at significantly earlier ages, which is associated with a higher fat mass later in life.
Exclusive breastfeeding in the first five months of life significantly protected children from becoming obese, a protection that became stronger at older ages and in children with higher GRS.
For example, for boys in the higher GRS quartile (scores 7.5 or higher), exclusive breastfeeding until five months of age was associated with a reduced BMI by 1.14 kg/m2 at age 18. According to the researchers, this compensates for a 3.9-point increase in GRS.
For girls, the reduction was even greater, reaching 1.53 kg/m2, which is estimated to compensate for a 7-point increase in genetic risk.
Breastfeeding also significantly protected children with lower genetic risk from gaining weight, but the effect was not as strong as in children with the highest genetic risk.
Exclusive breastfeeding significantly delayed the age of adiposity peak among those with average to high GRS scores, and delayed adiposity rebound in girls of all GRS scores. A lesser delay was seen in boys, not reaching statistical significance.
While exclusive breastfeeding for five months had the strongest protective effects, children who were exclusively breastfed for three months or breastfed, but not exclusively, for five months also had significant reductions in BMI variation caused by GRS.
“Our study demonstrates the role of the duration and exclusivity of breastfeeding in reducing BMI increases during childhood and adolescence resulting from adverse genetic effects,” the researchers wrote.
“This research suggests breastfeeding should be a priority for babies who are most at risk to set them on the right path for growth and development and to reduce the risk of obesity-associated diseases as adults,” added Stephen Lye, executive director of the Alliance for Human Development at the LTRI and a study co-author.
More research is now needed to understand the biological mechanisms behind the protective effects of breastfeeding, the scientists said.
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