The Medical Research Council (MRC) has helped to improve scientists' knowledge of why some girls go through puberty at an earlier age.

A recent study that involved an international group of researchers, including MRC members, identified 30 of the genes partly responsible for female sexual maturity.

The MRC said the genes also play a large role in determining how fat is metabolised, thus providing new links between younger-age puberty and a bigger obesity risk.

Some of the organisation's researchers were involved with the study, as were scientists from across the globe. It investigated 100,000 women and discovered specific genes in charge of hormone regulation and the development of cells.

Dr Ken Ong of the MRC epidemiology unit in Cambridge is senior author of the research - published in the journal Nature Genetics - and said it is now clear that being overweight and starting puberty at an earlier age are "intricately linked".

"If rates of childhood obesity continue to rise we will see many more girls reach puberty at young ages. Conversely, efforts to prevent or reduce childhood obesity will help avoid early puberty," he added.

The NHS currently recommends a minimum of 60 minutes' exercise every day for children, in order to keep active.