Is Your Furnace Making You Fat?

Popular media went into overdrive this week with stories about your furnace making you fat. Before you turn the heat down too far, stop, take a deep breath, and think about what the research really tells us. The stimulus for reports of the new thermostat diet was a review article published for early view online by Trends in Endocrinology and Metabolism.

The authors present a theory and supportive research findings suggesting to make the following points:

  1. Tightly controlled temperatures might increase our susceptibility to obesity.
  2. Exposure to mildly cold temperatures (>64ºF) increases energy expenditures.
  3. Temperature fluctuations within a range of 64º to 77ºF can be beneficial.
  4. Highly controlled indoor temperatures are costly.

This is all interesting stuff. Cold exposure increases brown fat tissue, which in turn burns more energy. Brown fat is a hot topic in obesity research that’s yielding important insights into energy balance regulation and obesity.

But what we don’t have yet is any cause and effect data — any evidence that cold exposure yields a meaningful net benefit for a healthier body weight. Nor do we have evidence of a net health benefit for increased cold exposure.

Is your furnace making you fat? Maybe…or maybe not. If you want to save some money by letting your indoor temperature vary a little, that’s fine. That’s reason enough.

Arya Sharma summarized it well:

So while my Dutch colleagues may be fascinated by the idea that turning down our ambient temperatures may help us burn a few calories – I am not holding my breath to this “solution” to the obesity epidemic.

Also, given that the vast majority of people with excess weight actually live in places where the only option to experience “colder temperatures” would be through more air-conditioning – this is not even a proposal that would make any environmental sense.

Well said.

Click here to read more in Salon, here to read the review article, here to read the commentary in Dr. Sharma’s Obesity Notes, and here to read new research on brown fat activation in PLOS One.

Fireplace 3, photograph © Enoch Ross / flickr

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