Study: Dieting may damage teenage girls' bones

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 that 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 girls.

In girls, an 11lb (5kg) increase in fat mass was associated with an 8% increase in the circumference of the tibia (lower leg bone).

As girls tend to have higher levels of fat than boys, even when they are normal weight, the findings suggest fat plays an important role in female bone development.

Building strong bones in youth is particularly important for women, as they are three times more likely to develop osteoporosis, and suffer up to three times more hip fractures than men.

Professor Jon Tobias, leader of the research, says: “There is a good deal of pressure on teenage girls to be thin, but they need to be aware that this could endanger their developing skeleton and put them at increased risk of osteoporosis.

“Many people think that exercise is the key to losing weight and building strong bones at the same time – but this may only be true up to a point.

“If you do a good deal of low impact exercise, such as walking, you will certainly lose fat but you may not be able to put enough stress on the bones to build them significantly. To offset the detrimental effect of fat loss on your bones, it may be important to include high impact exercise as well, such as running or jumping.”

The findings emerged from a study called Children Of The 90s, which enrolled 14,000 mothers during pregnancy between 1991 and 1992.

It has followed the youngsters and their parents in detail ever since.