By Riley Forbes
For those lucky enough to be in the northern hemisphere, winter is in full force and we’ve seen some bitter, and not so sweet, temperatures. Now, as a college student who passionately dislikes riding the campus bus, I’ve often rocked up to class with my nose frozen and dripping and my ears an attractive, tomato red. While I have often asked why I put myself through this torture, science may have an answer: brown fat.
Most people are aware that fat plays many roles in the body, including cushioning our organs, acting as insulation to maintain body temperature, and providing energy in times of caloric scarcity, but did you know that adipose (fat) tissue can vary in its metabolic activity?
As babies, we are born with a high proportion of body fat of which a large percentage is brown adipose tissue, also termed “brown fat”. This brown fat is extremely important for infants as it is highly metabolically active and allows them to maintain their body temperature by increasing heat production. Brown fat is a hot area of anti-obesity research as it has been speculated that “simply increasing brown adipose tissue (BAT) quantity and/or function may reduce body weight by dissipating excess calories”. A 2014 study, took mice following a high fat diet and exposed them to temperatures of approximately 40°F for 1-8 hours, three times a week. The results: metabolic rates increased 2-fold and activated BAT.
However, “in response, food intake increased to compensate for the increased energy expenditure” which did not lead to weight or fat loss (Ravussin et al., 2014). While these data may not convince one to stand outside naked in the snow, researchers did note that despite seeing no changes in fat loss, there was a statistically significant improvement in glucose management. Similarly, a 2016 study published in Cell Metabolism found that BAT aids in glucose clearance and, in animal models, reverses hyperglycemia and protects against diabetes.
Additionally, this study looked at a group of over 65,000 individuals exposed to outdoor temperatures, lower environmental temperatures corresponded with increased overall glucose control (Lee et al., 2016). As scientists continue to look for a solution to the obesity (and highly correlated, diabetes) epidemic, pharmacological methods of inducing brown fat activation may be a critical piece of the puzzle, due to the potential for maximizing the metabolism, increasing energy expenditure, a regulating glucose metabolism.
References:
Lee et al., 2016, Cell Metabolism 23, 602–609 April 12, 2016 ª2016 Elsevier Inc. http://dx.doi.org/10.1016/j.cmet.2016.02.007
Ravussin Y, Xiao C, Gavrilova O, Reitman ML (2014) Effect of Intermittent Cold Exposure on Brown Fat Activation, Obesity, and Energy Homeostasis in Mice. PLoS ONE 9(1): e85876. doi:10.1371/journal.pone.0085876