Grahame Hardie is Professor of Cellular Signalling at the Wellcome Trust Bio-Centre at the University of Dundee. He is distinguished for his work leading to the discovery of AMP-activated protein kinase. He has also shown its physiological role as a cellular fuel gauge, protecting the cell against environmental or nutritional stresses that deplete ATP. His findings have had a major impact in understanding the physiology of exercise and the pathophysiology of diabetes. He has revealed how the drug ‘metformin’ works in diabetes, a discovery with wide implications for health and disease, including obesity.