The increasing number of overweight and obese individuals has become one of the leading public health concerns in many countries around the world. Concomitant with this increase in the prevalence of obesity has been the rise in the number of weight-loss diets, many of which alter macronutrient composition, but with the majority focused on carbohydrate restriction. Low-carbohydrate diets are attractive because they promise rapid weight loss without having to count calories and compromise the consumption of many palatable foods. By contrast, traditional dietary recommendations for weight loss endorse a fat-restricted and calorie-restricted diet high in complex carbohydrates. Evidence indicates that low-carbohydrate diets could be better in terms of short-term weight loss relative to traditional low-fat diets, but little is known about their long-term utility and safety. Diets based on the traditional Mediterranean dietary pattern are becoming increasingly popular because of their healthful benefits, particularly regarding cardiovascular outcomes. Mediterranean diets encourage consumption of a variety of palatable foods, optimizing adherence and sustainability. In this Review we discuss the current evidence on the efficacy of low-fat, low-carbohydrate and Mediterranean dietary patterns for weight loss, their potential mechanisms of action and important clinical considerations.