The balance between energy expenditure and energy intake is vital to maintaining stable body weight. Therefore, understanding the processes that contribute to energy expenditure is vital in order to interpret the results of studies into the causes and consequences of obesity.
While most mammals expend energy by exercising more, by shivering and by activating heat production in brown fat (a process called non-shivering thermogenesis), the relative importance of each of these is not well understood.
In research published in the journal Cell Metabolism, studies led by Dr Sam Virtue and Professor Vidal-Puig at the University of Cambridge Metabolic Research Laboratories Disease Model Core demonstrate that how much a mouse moves does not appear to affect how much energy it expends at temperatures below its thermal neutral zone (the environmental temperature at which an animal does not need to make heat in order to maintain body temperature). For mice, the thermal neutral zone is 30˚C, and the study shows that, below this temperature, increased energy expenditure from activity may be compensated for by reduced heat production from other sources such as non-shivering thermogenesis in brown adipose tissue.
As most studies take place below 30˚C, this has important implications for interpreting the results of studies into why some mice are lean or obese and, ultimately, understanding human obesity.
The study is published in the following article: Below thermoneutrality, changes in activity do not drive changes in total daily energy expenditure between groups of mice Virtue S, Even P, Vidal-Puig A. Cell Metab. 2012 Nov 7;16(5):665-71. doi: 10.1016/j.cmet.2012.10.008 PMID: 23140644