Short-term starvation in the obese induces metabolic acidosis and increased calciuria resulting in severe negative Ca balance. Oral administration of 5 g Ca-lactate daily is capable of correcting acidosis, reducing calciuria and providing the body with 650 mg Ca daily, thereby maintaining a positive Ca balance throughout the period of starvation. We therefore propose administering this amount of the preparation to obese individuals during starvation as a simple and cheap preventive measure against bone demineralisation.