New research, published in the journal Pediatrics, shows obesity is the single largest predictor of earlier onset puberty in girls, which is affecting white females much sooner than previously believed.

This multi-institutional study only strengthens a growing body of research documenting the earlier onset of puberty in girls of all races.

“The impact of earlier maturation in girls has important clinical implications involving psychosocial and biologic outcomes,” said Frank Biro, MD, lead investigator and a physician in the Division of Adolescent Medicine at Cincinnati Children’s Hospital Medical Center. “The current study suggests clinicians may need to redefine the ages for both early and late maturation in girls.”

Girls with earlier maturation are at risk for numerous challenges, including lower self-esteem, higher depression rates, norm-breaking behaviors and lower academic achievement. Early maturation also results in higher risks of obesity, hypertension and several cancers of which include breast, ovarian and endometrial cancer.

Researchers at centers in the San Francisco Bay Area, Cincinnati and New York City examined the ages of 1,239 girls at the onset of breast development and the impact of body mass index and race/ethnicity. The girls ranged in age from 6 to 8 years at enrollment and were followed at regular intervals from 2004 to 2011. Researchers used well-established criteria of pubertal maturation, including the five stages of breast development known as the Tanner Breast Stages.

The girls who participated were followed through multiple regular visits for each girl. Researchers said this method offered a good perspective of what happened to each girl and when it occurred.

Researchers found the respective ages at the onset of breast development varied by race, body mass index and geographic location. Breast development began in white, non-Hispanic girls, at a median age of 9.7 years, earlier than had been previously reported. Black girls continue to experience breast development earlier than white girls, at a median age of 8.8 years. The median age for Hispanic girls in the study was 9.3 years, and 9.7 years for Asian girls.

Body mass index was a much stronger predictor of earlier puberty than either race or ethnicity. Although additional research is still needed to confirm the exact environmental and physiological factors behind this phenomenon, researchers concluded that the earlier onset of puberty in white females is most likely caused by greater obesity.

This study was conducted through the Breast Cancer and Environmental Research Program which was established by the National Institute of Environmental Health Science.