Longevity Briefs: Run Cooler, Live Longer?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: The resting or basal metabolic rate (BMR) refers to how many calories your body needs to burn to support basic bodily functions. About 65% of our daily calorie intake goes towards the basal metabolism, with the rest going towards physical activity and digestive processes. 

Research generally shows that species with shorter lifespans have higher resting metabolic rates. Research also shows that different people, even those of similar age, sex and body weight, can have different BMRs – some people just ‘run hotter’. Can you change your resting metabolic rate on purpose, and might doing so extend your lifespan?

What did the researchers do: In this study, researchers investigated the relationship between BMR and lifespan among over 360 000 participants from the UK biobank. To do this, they used Mendelian randomisation, in which researchers look at genetic predictors of BMR, rather than measuring participants’ BMR itself. This helps reduce the risk of confounding factors influencing the results. For example, diabetes could increase your metabolic rate rather than the other way around, but diabetes cannot give you a gene variant for increased metabolic rate. Therefore, if people with such a gene variant get more diabetes, we can be pretty sure that increased metabolic rate contributes to becoming diabetic.

Researchers then compared genetic predictors of BMR to parental attained age (how long the participants’ parents lived) as a proxy for the expected lifespan of the participants.

Key takeaway(s) from this research:

• Lower genetically predicted BMR was associated with increased parental lifespan, and this association was stronger in women than in men.
• Genetically predicted BMR had no association with lifespan of the top 10% longest-lived.
• Some practices like calorie restriction result in a lower BMR, which could mediate some of their apparent health benefits.

The researchers found that having a lower genetically predicted BMR was associated with increased parental lifespan, and that this effect seemed to be stronger in women than in men. This is probably related to men having higher BMR on average, due to having increased muscle mass for a given weight. When looking specifically at the 10% of participants with the longest-lived parents, BMR had no association with lifespan, suggesting that it might not be as important for reaching a more advanced age.

Many previous studies have linked age-related diseases with increased metabolic rate in humans. There are many possible explanations for this. Inflammation, chronic diseases or the drugs used to treat those diseases could boost BMR, rather than the other way around. However, this study seems to suggest that a higher BMR itself may shorten human lifespan, and could be a target for lifespan extension. 

Examples of practices that lower BMR include calorie restriction and limiting protein intake. However, many practices that raise BMR (such as building more muscle through resistance training) are very clearly a net benefit to longevity, at least up to a point. More investigation is needed to understand the mechanisms of BMR and its true impact on human lifespan.