The treatment of obesity with a very-low-calorie liquid-formula diet: an inpatient/outpatient comparison using skimmed-milk protein as the chief protein source.

Fifty obese patients were givena 1.34 MJ (320 kcal) formula diet (containing 44 g/day carbohydrate, milk protein supplying 24--29 g protein/day in a total of 31 g/day, fat 2 g/day and the RDA of minerals and vitamins) for four to 12 weeks, either as inpatients (22) or outpatients (28). This regime was followed by a 3.35 MJ (800 kcal) conventional diet as outpatients. All but six outpatients completed the trial. Substantial weight losses were achieved in all patients with a total mean loss of 8.4 kg at four weeks and 11.0 kg at eight weeks. At four weeks the mean weight loss was 9.6 kg for inpatients and 7.2 kg for outpatients (P less than 0.05). There was no statistical difference in weight between the groups at eight weeks. Patients who continued on the 1.34 MJ formula diet for 12 weeks continued to lose weight but those on the 3.35 MJ conventional diet did not. Nitrogen-balance studies were carried out on the inpatients. During the first four weeks there was a small net loss of nitrogen (56 g, equivalent to 350 g protein) but equilibrium was achieved by the fifth or sixth week. There was no evidence of protein deficiency as judged by unchanged serum total protein, albumin, haemoglobin, RBC and PCV. Equilibrium between intake and excretion of sodium and potassium was also achieved throughout, and serum electrolytes were unchanged. A large number of other routine clinical and laboratory tests showed the treatment was safe. Serum bilirubin was elevated (18--48 per cent) and increased slightly above normal in two outpatients. Serum cholesterol was decreased by 21 per cent and triglycerides by 45 per cent after three weeks. Serum lipids in hyperlipaemic patients were normalised. It is concluded that the very-low-calorie formula diet provides a safe and very effective method of weight reduction, and the advantages of hospital compared with outpatient treatment are small.