BACKGROUND: The prevalence of obesity has increased rapidly in most developed countries in the last decades, and this rise is now spreading to developing countries. Childhood obesity is also increasing. The UK government has set a target to halt the rise in childhood obesity by 2010. Dietary recommendations are a central component of any comprehensive weight-loss programme. A low-fat energy-restricted diet is the conventional therapy for obesity, but alternative dietary interventions have been proposed in recent years. METHODS: We conducted a systematic review to assess dietary intervention studies designed to reduce weight in childhood and adolescence. The studies included overweight or obese children or adolescents in which there was a comparison group and change in body weight or BMI was reported. RESULTS: We identified only nine such studies, seven of which were randomized. Six were conducted in the USA, two in Cuba, and one in France. Low-carbohydrate and low-glycaemic-index diets appeared to be at least as effective as energy-restricted low-fat diets for short-term weight loss, but most studies were too small to be informative, and none provided evidence on long-term weight control. CONCLUSIONS: There is a marked mismatch between the public health importance of childhood obesity and the number and quality of the studies conducted so far to assess dietary interventions for weight reduction in childhood and adolescence, and little evidence to support the current recommendation of a low-fat energy-restricted diet. There is an urgent need for well-designed intervention studies of the long-term effectiveness of alternative diets to provide a basis for evidence-based recommendations.