John Speakman is a Professor at the Shenzhen Institute of Advanced Technology in Shenzhen, China and also at the University of Aberdeen in Scotland, UK. He has been working on energy balance and obesity for more than 40 years. He has been using the doubly-labelled water method for most of that time and has published many papers on the energy demands of free-living animals and humans. He was a driving force behind establishment of the IAEA DLW database that has led to many novel insights into human energy demands. His recent work has focused on using the mouse as a model to understand macronutrient effects on energy balance, and the impacts of calorie restriction. He has also established a unique human metabolic facility in Shenzhen. He published over 650 scientific papers including 14 in Nature/Science, and was featured twice on the cover of Nature. He is a foreign member of the US National Academy of Sciences, an academician of the Chinese National Academy of Sciences and a Fellow of the UK Royal Society. In 2020 he was awarded the US Obesity Society TOPS award and in the same year was also awarded the Osborne-Mendel prize by the American Society of Nutrition for basic research. In 2023 he was awarded the Society for Endocrinology Dale medal, and in 2024 the American Physiology Society Solomon Berson award.