The concept sounds intriguing: turn down the thermostat a couple of notches and you’ll lose weight. Let’s investigate if that could work.
You may remember that a long, long time ago I wrote about the futility of drinking cold water to lose weight. If you don’t want to head over to my (I dare to say) highly interesting article from back then, let’s just say that the calorie-burning effect of the body having to heat up the water is so small you can classify it under non-existent.
But what about the other direction? What if you don’t put something cold inside the body, but surround the body with cold outside?
Already in 2011 a study examined if ambient temperature, television watching or sleep restriction could influence people’s weight negatively. Lo and behold, that study found that indeed room temperature was connected to obesity. In the words of the researchers:
[A] twofold increased risk for both incident obesity and hyperglycemia was estimated in subjects living at an indoor temperature >20°C.
That study made its rounds on the usual news outlets, but most, if not all, forgot to include an important note that came toward its end:
It might be hypothesized that metabolic processes are favorably affected by an ambient temperature within the thermal neutral zone, that is, not requiring energy expenditure to be allocated to maintaining a constant body temperature. However, no evidence exists to support this and socioeconomic factors might confound these associations.
In other words: they couldn’t be sure if room temperature and weight really were related to one another, or if overweight people simply prefer to live in warmer rooms.
Of Brown Fat And Cold Rooms
Now we get two new studies that give us data a bit more reliable. Recently published in the Journal of Clinical Investigation, they put their focus on “brown fat” – a form of fat that burns energy to help keep you warm.
In the first of these two, Dutch researchers showed that when people are exposed to cold, the body’s first reaction to keep up its temperature are the usual “muscle contractions” (er, “shivering” for the rest of us), but then something interesting happens: the longer people had a chance to get used to the cold, the less they shivered. Not because their bodies felt the cold any less, but because they had switched to a different means of producing warmth. That, it turned out, was an increased activity of the brown fat.
The second study went down a similar road, but also measured how much influence this could have on people’s body weight. Here it gets really interesting: the group that for six weeks was exposed to a daily 2h at 17 °C (62.2 °F) increased its resting energy expenditure and decreased body fat by 5.2%. The control group that spent the daily two hours at 27 °C (80.6 °F) didn’t experience any fat loss.
Are We Too Coddled?
What do you make of this? Could it be that central heating did its part in influencing our body weight? After all, most people today like to keep ambient room temperature at about 21 °C (70 °F). A hundred years ago (sometimes less) it were ovens or fireplaces that kept houses warm and in the mornings these were stone cold. To get warm you and your body had to work more and, of course, you also had to shovel the coals or hack the wood that got the oven going again.