Klaas Westerterp is Professor of Human Energetics at Maastricht University. His field of expertise is energy metabolism, physical activity, food intake and body composition, and energy balance under controlled conditions and in daily life. He is member of the Editorial Board of the journal Nutrition and Metabolism (London), the European Journal of Applied Physiology, the European Journal of Clinical Nutrition, and Editor-in-Chief of the Proceedings of the Nutrition Society.