The development of very-low-calorie diets (VLCD) over the lats 50 years is described, from the early work of the Pittsburgh group in 1930, using conventional food, to the present day liquid-formula diets containing all essential nutrients. Recent work has been concerned with the protein requirements of obese patients consuming 200-400 kcal (0.8-1.6MJ) VLCD. Independent studies indicate that the protein requirement is about 40-55 g/day without carbohydrate, and about 25-30 g/day when carbohydrate (30-45 g/day) is included. Although some workers use VLCD consisting only of protein, the author prefers those also containing carbohydrate because they prevent excessive ketosis, hyperuricemia, diuresis, electrolyte loss, re-feeding oedema, and may improve muscular endurance. Numerous clinical trials have shown VLCD to be highly effective in about 80 per cent of outpatients and give an average weight loss of 2 kg/week which is comparable to that seen in complete starvation. Clinical studies of up to 16 weeks and longer in numerous medical schools in Europe have demonstrated their safety in patients under medical supervision. Whilst the achievement of a normal body weight in most obese patients is now a reality, the main problem for the future is to achieve permanent weight loss.