[6] Between 2011-2020, he was  a '1000 talents' Professor at the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, in Beijing, China, where he ran the molecular energetics group.

[citation needed] Speakman was educated at Leigh Grammar School, near Manchester, and then went to the University of Stirling where he was awarded a BSc in Biology and Psychology in 1980 and a PhD in 1984 for research on the energetics of foraging in wading birds.

Speakman's work focuses on the causes and consequences of variation in energy balance, and in particular the factors that limit expenditure, the genetic and environmental drivers of obesity and the energetic contribution to ageing.

[6] He is an internationally recognised expert in the use of isotope methodologies to measure energy demands and has used these methods on a wide range of wild animals, model species and humans.

A paper by Pontzer, Yamada and colleagues utilising this database, on which Speakman was a co-corresponding author, summarised the metabolic rates of humans between 8 days and 96 years old, was published in Science in August 2021.

[14] With Aberdeen colleague Ela Krol, among others, he has published a series of over 30 papers in the Journal of Experimental Biology, which culminated in a novel hypothesis that animal energy expenditure is limited by the capacity to dissipate body heat.

[15] The idea is claimed to have wide implications for our understanding of many aspects of ecophysiology and ecology – such as limits on range distributions, maximum possible sizes of endothermic animals e.g. dinosaurs, Bergmann’s rule, effects of climate change etc.

[24] Speakman was co-author with Patrick Butler, Anne Brown and George Stevenson of the textbook Animal Physiology published by Oxford University Press in 2020.