For a particular metabolic rate, having a lower body temperature would extend your lifespan.
In biology, the phrase “live fast, die young” does not mean living fast and risky lifestyles lead to accidents and premature deaths, rather, it describes the observation that animals with high metabolic rates (“living fast”) tend to die sooner than those with a slow metabolism.
However, within a species, the link between metabolism and lifespan is less clear. Generally, interventions that extend life, are in accordance with the idea of “live fast, die young”. For example, reducing the average daily caloric consumption leads to lower metabolism and longer life. Yet, activities like exercising increases metabolism, but on average, it seems to allow people to live longer.
A problem in figuring out the effect of metabolism on lifespan is that metabolism is often linked to changes in body temperature. Broadly, low metabolic rates are associated with low body temperature. So, when mice under caloric restriction live longer, it is not immediately clear if the extended lifespan is due to lower body temperatures or the lower metabolism caused by caloric restriction.
Recently, a research team from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences, Wenzhou University, and the University of Aberdeen, have found that body temperature influences lifespan to a greater degree than metabolism.
In order to decide which factor is more important, the researchers used an unusual situation where body temperature and metabolic rate move in the opposite direction.
It is known that when exposed to hot ambient temperatures, the body temperature of small mammals increases while their metabolic rate decreases. “We found that exposing the rodents to these conditions shortened their lifespans. Lower metabolism didn’t lengthen their lives, but higher temperatures shortened it,” said Professor John R. Speakman from SIAT, a co-corresponding author of the study.
In this study, with mice and hamsters exposed to high temperatures, the researchers had small fans blowing air over them. This prevents the mice and hamsters from having high body temperatures while leaving their metabolism unaffected. The researchers observed that this situation reversed the effect of high ambient temperature on their lifespan.
From the results, the researchers conclude that body temperature seems to be a more important mediator of lifespan than metabolic rate.
“We separated the effect of body temperature on lifespan from [the] metabolic rate in two species of small rodents exposed to high temperatures. We are excited about the findings, particularly that using small fans to blow air over the animals reversed the effect of high ambient temperature on life span by decreasing body temperature without changing [the] metabolic rate,” said Zhao Zhijun from Wenzhou University, who was the first and co-corresponding author of this study.
Source: Zhao et al. (2022). Body temperature is a more important modulator of lifespan than metabolic rate in two small mammals. Nature Metabolism, 1-7.