Background: Low-energy diets, ideally in combination with increased energy expenditure through physical activity, are the mainstay of obesity treatment. Very low-energy liquid diets (VLEDs) were developed to provide a safe alternative to starvation, with only a modest attenuation in the rate of weight loss. Aim: This paper considers the evidence concerning the efficacy of both commercial and milk-based total liquid diets, which provide a maximum of 800 kcal/day. Results: Long-term users of low-energy formula diets are a self-selected group who find these preparations acceptable. In these subjects early compliance is often good and weight losses of 8–10 kg in approximately 4–8 weeks are regularly reported. This compares favourably with acute weight losses using other treatment methods. However, there are concerns regarding the composition of tissue lost and the long-term maintenance of weight loss. Conclusion: VLEDs are a proven success in achieving significant short-term reductions in body weight. A subset of patients achieve long-term weight loss. There is evidence to suggest that meal replacements may make a contribution to the maintenance of weight loss in some individuals. Evaluation of integrated programmes using these methods for weight loss and long-term weight control is required.