MY nine-year-old daughter is rather overweight and has just started her periods. Could her weight and the early onset of puberty be related, or is it just a coincidence?

Professor Jonathan Pinkney of Plymouth University and Peninsula Schools of Medicine and Dentistry, recently led a study into the link between obesity in the young and the lowering of age of puberty.

He says: “This is relatively unusual, but by no means rare, since a few per cent of girls have begun periods by this age. It could of course be coincidence, but it’s more likely that the two are related.

“In the 19th Century, the average age at which girls’ periods started was around 16 years, compared with a current average of around 12 years. We found evidence that weight gain before age ten was associated with reduced blood levels of a protein called sex hormone binding globulin (SHBG) which controls the action of powerful sex hormones in the body.

Young overweight girls have lower levels of SHBG and this appears to be one factor that’s probably responsible for earlier puberty.