aInstitute of Diabetes and Clinical Metabolic Research, Kiel, Germany

bObesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, Arizona, USA

cDepartment of Information Engineering, University of Pisa, Pisa, Italy

Correspondence to Paolo Piaggi, PhD, FTOS, Obesity and Diabetes Clinical Research Section, National Institute of Diabetes and Digestive and Kidney Diseases, 4212 N 16th Street, Phoenix, AZ 85016, USA. Tel: +1 602 200 5306; fax: +1 602 200 5335; e-mail: [email protected]