Deliberate cold exposure can increase your overall core metabolic rate. The higher your metabolic rate, the more energy your body requires to maintain its normal functioning processes (via intake of calories/kilojoules or burning of fat stores) (21). Cold water immersion triggers the body’s temperature regulation mechanisms which require energy largely derived from fat cells. There are three different types of fat cells: white, beige and brown (22). White fat cells have a low metabolic output, whereas beige and brown fat cells have a high metabolic output and are considered “good” fat cells. When activated by cold exposure, beige and brown fat cells “burn” energy and create heat (referred to as thermogenesis) that helps maintain body temperature (23). People with higher levels of beige/brown fat cells require more energy to maintain normal functioning processes (24) – aka. they have a higher metabolic rate. Additionally, deliberate cold water immersion triggers release of norepinephrine, which is known to bind to low-metabolic-output white fat cells and help convert them into high-metabolic-output beige and brown fat cells (25)(26). Most significantly, this process of activation and conversion has been well-documented as continuing for a period of at least 24-hours after plunging (1).

1. Sramek P, Simeckova M, Jansky L, Savlikova J, Vybiral S. Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology. 2000;81(5):436-442. doi:https://doi.org/10.1007/s004210050065

21. Better Health Channel. Metabolism. Better Health Channel. Published 2012. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/metabolism

22. Marcin A. Brown Fat: What You Should Know. Healthline. Published January 22, 2018. https://www.healthline.com/health/brown-fat

23. Cohen P, Spiegelman BM. Brown and Beige Fat: Molecular Parts of a Thermogenic Machine. Diabetes. 2015;64(7):2346-2351. doi:https://doi.org/10.2337/db15-0318

24. Torgan C. Insights into Energy-Burning Fat Cells. National Institutes of Health (NIH). Published April 30, 2015. https://www.nih.gov/news-events/nih-research-matters/insights-into-energy-burning-fat-cells

25. Wein H. How brown fat improves metabolism. National Institutes of Health (NIH). Published September 9, 2019. https://www.nih.gov/news-events/nih-research-matters/how-brown-fat-improves-metabolism

26. Saito M, Matsushita M, Yoneshiro T, Okamatsu-Ogura Y. Brown Adipose Tissue, Diet-Induced Thermogenesis, and Thermogenic Food Ingredients: From Mice to Men. Frontiers in Endocrinology. 2020;11. doi:https://doi.org/10.3389/fendo.2020.00222