Teenage girls dieting to reach "size zero" may be putting their bones at risk.

Fat mass plays an important role in building bone, especially in girls, a child development study found. Experts have warned that the pressure to be thin could cause long-term harm to their skeletons.

The team from Bristol University looked at more than 4,000 young people aged 15, using sophisticated scanning techniques which calculated the shape and density of their bones, as well as how much body fat they had. Those with higher levels of fat tended to have larger and thicker bones. This connection was "particularly marked" in the females.

In girls, an 11lb (5kg) increase in fat mass was associated with an 8 per cent increase in the circumference of the tibia. Building strong bones in youth is particularly important for women, as they are three times more likely to develop osteoporosis than men. The findings emerged from a study called Children Of The 90s, which enrolled 14,000 mothers during pregnancy in 1991-92.