1. Department of Internal Medicine, University of Pisa, Pisa, Italy
2. CNR Institute of Clinical Physiology, Pisa, Italy
3. Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
4. Division of Bariatric Surgery, Santa Chiara Hospital, Pisa, Italy
5. CNR Institute of Biomedical Engineering, Padua, Italy.