Birth order may be to blame for weight issues, especially in first-borns, according to a recent study.
Research published online in the Journal of Epidemiology & Community Health found that first-born women are more likely to be overweight/obese as adults than their second-born sisters. The study is the largest of its kind in women. The researchers wanted to find out if birth order affected adult women's height and weight as it appears to among adult men, reports dbtechno.com.
"Ours was not only the largest study of birth order effects on women, but was also the only one focusing specifically on sibling pairs, to largely account for genetic factors and the early life environment," wrote Wayne Cutfield, a researcher at the Liggins Institute at the University of Auckland and the lead author of the women's study, according to the Washington Post.
A change in the blood supply to the placenta between first and later pregnancies, with the vessels more narrow in the first pregnancy, could reduce the nutrient supply to the fetus, Cutfield hypothesizes. This in turn, reprograms the regulation of fat and glucose, so that in later life the individual is at risk of storing more fat and having insulin that works less effectively, reports CBS News.
"Our study corroborates other large studies on men, as we showed that firstborn women have greater BMI and are more likely to be overweight or obese than their second born sisters," Cutfield writes, concluding that, "the steady reduction in family size may be a contributing factor to the observed increase in adult BMI worldwide, not only among men, but also among women," reports dbtecno.com.
