Early puberty not cause of obesity

The belief that girls who start menstruating before age 12 will be overweight later in life is unfounded, a new study reports.

Because excess body fat has been found to jump-start puberty, with some larger girls starting their periods before age 12, some doctors believed the reverse could also be true -- perhaps girls who matured at an earlier age faced a higher risk of becoming overweight later.

That belief led some doctors to focus on delaying puberty as a way to combat obesity, said researchers from Tufts University School of Medicine in Boston.

“For the parents of a girl who is not overweight and who gets her first period early, it doesn’t mean she’s at increased risk for being overweight as an adult,” said Aviva Must, the study’s lead author.

The report was based on data from the Newton Girls Study, which followed 700 girls from the small Massachusetts city beginning in 1965. Researchers also contacted roughly 450 of the participants when they reached an average age of 42.

The study was presented at a conference on back-to-school health issues sponsored by the American Medical Assn., and will be published in an upcoming issue of the journal Pediatrics.