“End your sauna session on cold to burn more fat.”

The research found this

Susanna Søberg's team published a study of Danish winter swimmers in 2021, and Andrew Huberman named a rule of ending on cold after her in a 2022 podcast episode.1Source 1 · Cross-sectional studyAltered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming menSøberg S, Löfgren J, Philipsen FE, et al.. Cell Reports Medicine, 2021.Read the paper ↗PubMed ↗2Source 2 · PodcastUsing Deliberate Cold Exposure for Health and Performance (episode 66)Huberman A. Huberman Lab podcast, 2022.Read the page ↗ People now call it the Søberg principle.

The paper doesn't contain the rule. Its full text says nothing about finishing on cold, and none of its experiments put heat and cold in any order.1Source 1 · Cross-sectional studyAltered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming menSøberg S, Löfgren J, Philipsen FE, et al.. Cell Reports Medicine, 2021.Read the paper ↗PubMed ↗ The authors speculated that heat acclimation from the swimmers' 57 minutes of sauna a week might explain why they ran cooler over 24 hours and showed no brown fat activity at a comfortable temperature.

Researchers haven't compared a cold finish with a warm one for energy use or brown fat. A 2013 meta-analysis of contrast water therapy noted whether each trial ended hot or cold and never analyzed its results by that.3Source 3 · Meta-analysisContrast Water Therapy and Exercise Induced Muscle Damage: A Systematic Review and Meta-AnalysisBieuzen F, Bleakley CM, Costello JT. PLoS ONE, 2013.Read the paper ↗PubMed ↗ A 2026 systematic review of 21 contrast studies reported no energy or brown fat outcomes. It did notice that blood pressure fell after sessions more often when heat came last, though the authors drew that pattern from comparing different studies.4Source 4 · Systematic reviewCardiometabolic effects of contrast therapy: A systematic reviewde Haan V, Plasqui G, Pallubinsky H. Experimental Physiology, 2026.Read the paper ↗PubMed ↗

Cold raises energy use both in the water and during rewarming. After 48 minutes of cycling and a seated rest, 21 trained men sat waist-deep in 10°C water for 15 minutes. At the end of the immersion their oxygen use was 7.16 ml/min/kg against 4.83 without it.5Source 5 · Crossover trialMechanism involved of post-exercise cold water immersion: Blood redistribution and increase in energy expenditure during rewarmingGiraud D, Pomportes L, Nicol C, et al.. Temperature, 2024.Read the paper ↗PubMed ↗ That gap works out to roughly 0.8 kcal a minute at that point, and the authors describe the rewarming that followed as metabolically costly.

In a 2026 trial in Wales, every sauna break on the dip day began with 90 seconds in 19.9°C water, so the last hot round was followed by cold. Fifteen minutes into recovery, core temperature on the dip day ran 0.63°C lower than on the air-only day, and the study didn't measure energy use.6Source 6 · Crossover trialThermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaksOwen TF, Giles CJ, Leaney SF, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗