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Is it true that human basal metabolic rate increases under high temperatures? If so, why does this happen? What are the underlying biological processes that are activated in very warm climates?

I find it counterintuitive that the basal metabolic rate would increase in high heat. In cold climate body spends energy to heat it up. But with high temperature climate it seems logical to decrease the basal metabolic rate to conserve energy and avoid dissipating additional heat generated during biochemical processes within the body. Can you explain why the body actually experiences an increase in basal metabolic rate under these conditions?

I've been asked to put my prior research, here are my findings: Some articles (1) (2) says that BMR is actually become higher in heat. Sadly my expertise in medical sciences is zero, thus I cannot verify if these findings are 100% correct. These papers doesn't mention exact biological mechanisms that are activated under heat. There is beautiful picture in this paper about all heat adaptation mechanisms, but it doesn't contain any energy consumption rates for these ones.

Can anyone with real human biology knowledge point out what mechanisms consume energy and help lower body temperature?

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Is it true that human basal metabolic rate increases under high temperatures? If so, why does this happen? What are the underlying biological processes that are activated in very warm climates?

This is not an area I have any background in. However, looking at the articles you referenced I suspect whether this is true or not is not definitely known.

First note that your second reference Serano et al doesn't actually say that heat stress raises basal metabolism rate (BMR). Rather they were looking at a mutation in mice that causes an increase in BMR and noticed that they suffered more under heat stress. The wonder if this sort of mutation might be a helpful marker for humans that were more susceptible to heat stroke.

The first article you refer to, Saxton, does present evidence that heat stress did raise heart rate, respiration, and CO2 production. The author states that "The results support a hypothesis that the increase in metabolism occurring during heat stress is limited solely to that part of the metabolism defined as basal". They don't suggest any mechanism, and it seems they are only claiming support for increased BMR as a hypotheses, not a proven effect.

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