Researchers quizzed over 90,000 women in their late thirties on their bra sizes when they were aged 20. They then looked to see how many of the women had gone on to get diabetes.

The results showed women who wore 'B' cups at the age of 20 were 37 per cent more likely to have diabetes than those wearing 'A' cups.

For those in a 'C' cup at 20, the risks soared by 80 per cent, dropping to 64 per cent among those in a 'D' cup. It remains unclear why breast size might affect diabetes risks. But one theory is that fatty tissue in the breast, called adipose tissue, may be involved in making the body resistant to the effects of insulin.

Adipose tissue found around the stomach and on the back is already known to raise the risk of diabetes.

In a report on their findings, the researchers said: "We found a statistically significant link between bra cup size and the development of type two diabetes."

They said more research is needed but it may benefit doctors to include breast size measurements when assessing if a woman is at risk of diabetes.