https://pmc.ncbi.nlm.nih.gov/articles/PMC3405064/

> Nonetheless, average daily energy expenditure of traditional Hadza foragers was no different than that of Westerners after controlling for body size. The metabolic cost of walking (kcal kg−1 m−1) and resting (kcal kg−1 s−1) were also similar among Hadza and Western groups. The similarity in metabolic rates across a broad range of cultures challenges current models of obesity suggesting that Western lifestyles lead to decreased energy expenditure.

> So where does the energy burn in a sedentary population come from vs highly active Hadza tribe members?

P.S.: One theory I've seen is that the extra sedentary-spend is in the immune-system, which may have both beneficial and harmful effects, depending on whether it's doing useful work versus causing problems.