Girls who enter puberty earlier have an increased risk of obesity as they get older, according to research  published online Feb. 6 in the International Journal of Obesity. 

Prior studies have already established increased weight as a risk factor for earlier onset of puberty, though it was unclear if the findings in previous studies were influenced by age, ethnic background, diet and other factors.

Using the statistical technique Mendelian Randomization, researchers from Imperial College London in England sought to determine if there was a link between genetic variants to show the relationship between earlier puberty and increased body mass index (BMI).

Data was used from more than 182,000 women and researchers identified 122 genetic variants strongly associated with early onset puberty.

Researchers used a questionnaire to determine the age at which women had their first period. For the second part of the study, the researchers investigating data from the UK Biobank of more than 80,000 women to obtain BMI. The analysis exhibited a link between genetic variants and BMI. Women who had early puberty variants also had high BMI.

The researchers also found the same association in a third study cohort of more than 70,000 women.

"Some of these genetic variants are associated with earlier puberty and some with later onset, so by taking advantage of this we were able to investigate any association of age at menarche with BMI in adulthood,” said lead researcher Dipender Gill, DG, with the Imperial College London, and colleagues. "We're not saying that it's a genetic effect, but rather that by using these genetic variants as a proxy for earlier puberty, we are able to show the effect of earlier puberty without the impact of external factors that might confound our analysis. We performed a range of statistical sensitivity analyses to test the robustness of our findings and they remained strong through this, so within the limitations of the study design, we are confident of findings."