Some outtakes from the study:
* Total Energy Expenditure reduced by 7.7% in males, 5.6% in females.
* Basal Energy Expenditure reduced by 14.7% in males (!!), 2% in females**
* They adjusted for body composition by looking at fat-free mass, fat mass, and age as predictors.
* To check these observations a systematic review of literature on BMR from the US and Europe over the past 100 years has shown a decline of BMR by about 0.34 MJ. Consistent, but lower numbers than this study.
The study also outlines some potential contributors to the reduction of BEE such as diet, decreased immune function, but also methodological artefacts.
>In the early years, measurements of BMR were made by using mouthpieces to collect respiratory gases, and recently such devices have been shown to elevate BMR by about 6%. A second possibility is that early measurements paid less attention to controlling ambient temperature to ensure that individuals were at thermoneutral temperatures.
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I've personally suspected something like this about myself. Whenever I've tracked my calories, it seemed that my actual metabolic rate was a bit lower than the various calculators suggested. I chalked it up to poor calorie tracking and wrong activity level assumptions though.
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** not statistically significant, inclusion of one study caused the reduction to be only 2%, but there was no reason to discount the study