Low-carbohydrate diets have traditionally been regarded as non-evidence-based, fad diets. However, several research groups have now reported randomized trials of up to 1 year in duration in which weight loss with low-carbohydrate diets was compared with conventional low-fat, calorie-restricted diets. In general, the trials have shown better weight reduction at 6 months in the low-carbohydrate compared with the low-fat groups, but very little if any difference in weight loss at 12 months between the diet groups. Favorable changes in triglycerides and high-density lipoprotein (HDL) cholesterol were also noted in the low-carbohydrate groups. While the available results are intriguing, there are still unanswered questions about the safety and long-term efficacy of low-carbohydrate diets that will require larger and longer-term studies. This research is needed before low-carbohydrate diets can be routinely recommended to the general overweight and obese population. © 2005 International Life Sciences Institute.