Although overweight girls are more likely to start their periods earlier than their peers who are at or below normal weight, early menstruation is not by itself a risk factor for later obesity, according to a long-term study released this week.
In fact, it's more likely that excess body fat jump-starts puberty than the other way around. Additionally, girls who are overweight before their first periods are almost eight times more likely than their slimmer peers to be overweight as adults.
"It has been long known that if you are overweight as you grow up, you are more likely to begin puberty early," said Aviva Must, Ph.D., associate professor of Public Health and Family Medicine at Tufts University School of Medicine in Boston and lead author of the study, published in the September issue of the journal Pediatrics. "Girls who are overweight are more likely to have early menarche, or start their period, before age 12. I have been concerned that a widespread belief was forming that the timing of menarche was itself linked to later weight status."
This belief, which may have led physicians to focus on changing the timing of puberty as a way to combat adult obesity, was discounted by Dr. Must's findings. "These findings are significant because they show us where our efforts should focus: childhood obesity," said Dr. Must, who is also a scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts. She spoke today in New York City at the American Medical Association and National PTA media briefing, Back to School: Child and Adolescent Health.
The new paper used data from the Newton Girls Study, which followed a group of about 700 girls from a small city near Boston. The girls were recruited in 1965 and studied from before their first period through their 20th period. The girls or their mothers provided monthly reports, allowing researchers to accurately pinpoint their age at menarche. Most studies rely on subjects recalling the age at which they got their first period, which may be remembered with error, Dr. Must said.