Fit, Fat, & Cold

It is rare when I truly love something I write or an idea that I have. I tend to be hypercritical and continually play devil’s advocate with myself. And though that is likely a good thing for science, it often means I get less joy from the grueling process I put myself through. This new article, however, is the exception.

Dr. Alexandra Niclou and I recently published a commentary in Evolution, Medicine, and Public Health. In this article, we not only tear down the current concept and broad use of body mass index (BMI), but also present how the suite of features we typically see among cold climate populations may confer a metabolically healthy obese phenotype (or the fit and fat phenotype). The idea of a fit and fat phenotype has been around for a short while – it suggests that individuals can have a high BMI/high body adiposity but not suffer any of the cardiometabolic consequences often association with a high BMI/high body adiposity.

I have been percolating this idea for a fair amount of time since working through the data on reindeer herders, who despite having high BMI/body adiposity, have relatively healthy indicators of cardiometabolic health. There is a growing body of evidence, though not without controversy, that a metabolically healthy obese phenotype is a reality, rare, but a reality. I began to wonder how some of the interesting physiological and morphological variation we ascribe to cold climate populations may predispose these folks to a metabolically healthy obese phenotype.

Schematic representing how the different suite of morphological, physiological, and behavioral characteristics of cold climate populations may lead to a metabolically heathy obese phenotype.

In this paper, Alex and I work through the evidence and present a fit, fat, and cold hypothesis that still needs a great deal of testing. Theoretical though it may be, I think this is an intriguing possibility and one that could impact how individuals with high adiposity (and low adiposity) are treated by medical doctors.