The findings, based on data from more than 4,100 students at Minnesota middle schools and high schools, underline the negative effects of dieting and also appear to reflect a sizeable market opportunity increasingly used by supplement makers.

Research from the US shows that dieters following a low-carbohydrate regime are more likely to also take supplements and use functional foods than people not on a diet.

Indeed some supplement companies have directly targeted the nutritional deficiencies of this group. Wyeth recently launched a low-carb vitamin formula, while in the UK, Principle Healthcare has introduced a 'support pack' for low-carb dieters, containing a peppermint oil and parsley seed breath freshening capsule and omega-3 fatty acids to improve blood lipid levels.

The new study, published in the June issue of the Journal of the American Dietetic Association (volume 104, no 6), found that 57 per cent of girls were using at least one unhealthy approach to weight loss, such as fasting, skipping meals, smoking, or using laxatives, diet pills or diuretics.

These girls also had significantly lower intakes of fruit, vegetables, grains, calcium, iron, vitamins A, C, and B-6, folate and zinc than girls not trying to control their weight.

Among boys however, researchers saw no such impact as a result of dieting and fruit intake tended to be higher.