Healthy excursions outside the comfort zone

Comfort and health may be related but are no synonyms. In the last years, we enhanced our knowledge regarding health effects of temperature exposure outside the human thermal comfort zone. Mild cold and warm environments increase metabolism, thereby targeting obesity by counterbalancing excess energy intake. Furthermore, we recently showed that mild cold influences glucose metabolism. Ten days of intermittent mild cold exposure in type 2 diabetes patients significantly increased insulin sensitivity, and thereby glucose handling capacity with more than 40%. This is comparable to the best currently available pharmaceutical therapies. A new study in obese subjects confirms these findings. Does this mean that we have to suffer from discomfort in order to become healthy? Probably not. Firstly, prolonged temporal excursions outside the thermal comfort zone result in acclimatization and we show that both cold and heat acclimation go hand in hand with increased comfort ratings. Secondly, low or high temperatures in a dynamic thermal environment may be perceived as acceptable or pleasant and evoke alliesthesia. We advocate studying dynamic thermal conditions, link this to the adaptive comfort model, and monitor these conditions in actual living conditions. This information is needed to design both healthy, comfortable and energy-friendly indoor environments.