Inherited Burden? Early menarche in moms tied to obesity in kids

Women who reach puberty at an unusually early age are more likely to have children who are overweight, a study finds.

Earlier research had linked extreme obesity in childhood with early arrival of menarche, a girl’s first period, which marks the onset of puberty. That result caused scientists to suspect that fatty tissue imparts a hormonal impact that hastens menarche. Meanwhile, scientists noticed that early menarche runs in families.

In an attempt to clarify such relationships, pediatric endocrinologist Ken K. Ong of the University of Cambridge and his colleagues tapped into a database tracking the growth of 6,009 children born in England in the early 1990s. Using information supplied by the children’s mothers, the team divided the kids into groups according to their mothers’ ages at menarche. Children whose moms had reached that milestone of puberty the earliest—by age 11—were three times as likely to be obese at age 9 as were children whose mothers reached menarche after age 15. The heightened rate of obesity showed up in both sons and daughters, the researchers report in the April PLoS Medicine.

When making the comparison, the scientists accounted for differences in the mothers’ ages and educational levels. After further adjusting their calculations to account for weight differences among the mothers, the researchers found that children born to early-menarche women were twice as likely to be obese as were those born to late-menarche moms.

A closer look at medical records for 914 of the children chosen randomly from the group revealed that those born to early-menarche women were the most likely to gain significant excess weight by age 2 and to retain it throughout early childhood. The early weight gain in these children mostly reflected increases in fat rather than in muscle mass. Compared with kids born to late-menarche women, offspring of early-menarche mothers were, on average, taller in early childhood but not in later years.

Consistent with past studies, girls born to early-menarche women reached puberty earlier than other girls.

Although the study was designed only to show a correlation, it raises the question of whether children are programmed to take a specific growth path, says Ellen W. Demerath, an epidemiologist at Wright State University in Kettering, Ohio. “I buy it, though, that there could be genetic mechanisms involved,” she says.

Specifically, mothers who reach puberty early might pass on genetic traits to their children that affect appetite and satiety in infancy, Ong says. Or the moms might send signals to their offspring in utero.

Such predispositions might make evolutionary sense, at least in times of plentiful food, Ong says. In an era when women had many pregnancies and short life spans, he says, “reaching reproductive capacity early would be a benefit, as would having larger progeny.”

In modern times, when people live much longer, childhood obesity increases the risk of later health problems. That turns the spotlight on nutrition, particularly during infancy and early childhood, Ong says.

Endocrinologist Mary Horlick of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., says that she would like to see this study continue to track the families and to provide information on the next generation.