John Speakman is a British biologist working at the University of Aberdeen, Institute of Biological and Environmental Sciences, for which he was Director from 2007 to 2011. He leads the University's Energetics Research Group, which is one of the world's leading groups using doubly labeled water (DLW) to investigate energy expenditure and balance in animals. Speakman is well known for his work on obesity, in particular for criticising a long-established theory for obesity known as the thrifty gene hypothesis. With Aberdeen colleague Ela Krol, among others, he has published a series of over 20 papers in the Journal of Experimental Biology, known as the ‘limits’ series, which culminated in a novel hypothesis that animal energy expenditure is limited by the capacity to dissipate body heat. He was the first non-Chinese recipient of a ‘Great wall’ professorship from the CAS-Novonordisk Foundation (2011) and in 2015 was the first Briton ever to be awarded the Chinese Academy of Sciences medal for International cooperation. Speakman writes a monthly popular science column for the magazine ‘Newton’ (translated into Chinese by an ex-student Lina Zhang) and has also published two popular science books consisting of the compiled English versions of these articles.