Editing Basal metabolic rate (section)

===Research on individual differences in BMR===
The basic metabolic rate varies between individuals. One study of 150&nbsp;adults representative of the population in Scotland reported basal metabolic rates from as low as {{convert|1027|kcal|kJ}} per day to as high as {{convert|2499|kcal|kJ}}, with a mean BMR of {{convert|1500|kcal|kJ}} per day. Statistically, the researchers calculated that 62% of this variation was explained by differences in [[fat free mass]]. Other factors explaining the variation included [[fat mass]] (7%), age (2%), and [[experimental error]] including within-subject difference (2%). The rest of the variation (27%) was unexplained. This remaining difference was not explained by sex nor by differing tissue size of highly energetic organs such as the brain.<ref name="Johnstone">{{cite journal |vauthors=Johnstone AM, Murison SD, Duncan JS, Rance KA, Speakman JR, Koh YO |year=2005 |title=Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine |journal=[[American Journal of Clinical Nutrition]] |volume=82 |issue=5 |pages=941–948 |pmid=16280423 |doi=10.1093/ajcn/82.5.941|doi-access=free }}</ref>

A cross-sectional study of more than 1400 subjects in Europe and the US showed that once adjusted for differences in body composition (lean and fat mass) and age, BMR has fallen over the past 35 years.<ref name="speak">{{cite journal |vauthors=Speakman JR, et al. |year=2023 |title= Total daily energy expenditure has declined over the last 3 decades due to declining basal expenditure, not activity expenditure |volume=5 | pages=579–585 |journal=[[Nature Metabolism]] |issue=4 |doi=10.1038/s42255-023-00782-2|pmid=37100994|pmc=10445668 }}</ref> The decline was also observed in a [[meta-analysis]] of more than 150 studies dating back to the early 1920s, translating into a decline in total energy expenditure of about 6%.<ref name="speak"/>