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Here’s one I hadn’t heard before:
Increases in winter indoor temperatures in the United Kingdom, United States and other developed countries may be contributing to rises in obesity in those populations, according to [University College London] research published today.
Reduced exposure to cold may have two effects on the ability to maintain a healthy weight: minimizing the need for energy expenditure to stay warm and reducing the body’s capacity to produce heat.
In particular, the authors note, exposure to cold is thought to stimulate the production of the famous but elusive “brown fat” that burns calories to generate heat. The paper itself goes into great depth about the proposed mechanisms and the expected effect size. Two graphs that I found interesting; first, indoor temperature trends in the U.S. and U.K.:
I love that U.K. bedroom temperature data! I lived in an unbelievably leaky apartment in Montreal for a couple of years — it was the former “coach house” behind a grander building, so it had no insulation. We were paying for our own heat, and had no money, so we kept the thermostat in the living room down about 13-15 C, and didn’t bother heating the bedrooms, kitchen or bathroom. We kept a “guest blanket” on the couch for anyone foolish enough to visit. And both my roommate and I were pretty skinny throughout those two years…
This is the crucial data — 24-hour energy expenditure as a function of temperature. Could it make a difference? Maybe. But before anyone gets too upset about this, I should note that even the authors of the paper aren’t proposing that this is the cause of obesity — they’re just suggesting it could be one of the many contributing factors.