Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men
Susanna Søberg, Johan Löfgren, Frederik E. Philipsen, Michal Jensen, Adam E. Hansen, Esben Ahrens, Kristin Brønnum Nystrup, Rune D. Nielsen, Christine Sølling, Anne‐Sophie Wedell‐Neergaard, Marianne Berntsen, Annika Loft, Andreas Kjær, Zachary Gerhart‐Hines, Helle Hjorth Johannesen, Bente Klarlund Pedersen, Kristian Karstoft, Camilla Schéele
Abstract
The Scandinavian winter-swimming culture combines brief dips in cold water with hot sauna sessions, with conceivable effects on body temperature. We study thermogenic brown adipose tissue (BAT) in experienced winter-swimming men performing this activity 2-3 times per week. Our data suggest a lower thermal comfort state in the winter swimmers compared with controls, with a lower core temperature and absence of BAT activity. In response to cold, we observe greater increases in cold-induced thermogenesis and supraclavicular skin temperature in the winter swimmers, whereas BAT glucose uptake and muscle activity increase similarly to those of the controls. All subjects demonstrate nocturnal reduction in supraclavicular skin temperature, whereas a distinct peak occurs at 4:30-5:30 a.m. in the winter swimmers. Our data leverage understanding of BAT in adult human thermoregulation, suggest both heat and cold acclimation in winter swimmers, and propose winter swimming as a potential strategy for increasing energy expenditure.