Cold-water immersion (CWI), the practice of plunging into icy water, has gained popularity in wellness circles, praised for its supposed benefits to mental and physical health. But while many tout its positive effects on metabolism, fat loss, and mental well-being, researchers are still debating whether the benefits are as widespread as claimed. Recent scientific studies shed light on how our bodies respond to cold-water exposure and provide new insights into the health implications of this chilling activity.
One study published by Michael Boschmann and colleagues explored how drinking water could influence energy expenditure. Their findings revealed that consuming 500 ml of water increased metabolic rate by 30%, primarily by heating the water from 22°C to body temperature (37°C). The thermogenic response—burning around 100 kJ per 500 ml—was significant, especially for those looking at weight loss strategies. Interestingly, the study highlighted gender differences in energy use, with men burning lipids (fats) and women primarily utilizing carbohydrates to fuel this metabolic boost. This suggests that drinking more water could slightly augment energy expenditure during weight loss programs, although it is far from a magic solution.
Cold exposure has long been a test of human endurance, and the body’s response is an intricate dance of energy management. A separate study looked at how our body breaks down different fuels—glucose, glycogen (stored sugars), and fats—during cold stress. When exposed to cold temperatures, participants burned 2.6 times more energy than in a neutral environment. Fat played a starring role, accounting for about 50% of the total energy used, while muscle glycogen contributed 30%. Though glucose usage rose significantly, it only made up about 10% of energy expenditure.
This study highlights that during prolonged cold exposure, the body turns to fats and stored glycogen as primary fuel sources. For athletes or individuals in extreme conditions, this knowledge is crucial for maintaining body heat and preventing hypothermia. However, the study also raised concerns: individuals with low glycogen stores risk cooling down faster and experiencing increased vulnerability to cold.
The effects of cold-water immersion go beyond just energy expenditure. A third study examined how immersing participants in different water temperatures impacted heart rate, blood pressure, and hormone levels. At room temperature (32°C), heart rates dropped, blood pressure decreased, and stress hormones like cortisol diminished. However, as the water got colder, the body had to burn significantly more energy to maintain warmth—by 350% in water at 14°C. Stress hormones like noradrenaline spiked by 530%, showing the body’s natural fight-or-flight response to extreme cold.
Interestingly, cold-water immersion led to increases in certain hormones associated with energy regulation and blood pressure, such as aldosterone. The hormonal spikes also aligned with increased heart rate and blood pressure, a physiological reaction designed to protect vital organs and maintain core temperature.
While many studies show promising results regarding cold-water immersion, there is no clear consensus in the scientific community. The positive effects—improved metabolism, fat loss, and mental resilience—are often cited, but much of the research is conducted on small, homogeneous groups, such as experienced winter swimmers or healthy young individuals. Variability in water temperatures and exposure times also make it challenging to generalize the findings.
Despite these limitations, the growing body of evidence suggests that regular cold-water immersion can have benefits beyond just burning calories. It may improve insulin sensitivity, enhance stress management, and even boost immune function. But as with any health intervention, the outcomes depend on a person’s overall health, lifestyle, and individual response to cold exposure.
Cold-water immersion remains an intriguing area of study, with the potential for both physical and mental health benefits. From boosting metabolic rate to improving mood, the science behind cold exposure is slowly unraveling the mysteries of how our bodies respond to the chill. However, more research is needed to fully understand its long-term effects and who stands to benefit the most. Until then, CWI will continue to spark debate and interest among scientists and wellness enthusiasts alike.
Michael Boschmann et al. (2003). Water-induced thermogenesis. PMID: 14671205. DOI: 10.1210/jc.2003-030780. PubMed: Water-induced thermogenesis
J. Appl. Physiol. (2001). The Effect of Cold on Energy Use in Humans: A Breakdown of Glucose, Muscle Glycogen, and Fats. DOI: 10.1152/japplphysiol.00773.2001. Journal of Applied Physiology
Cold-Water Immersion and Its Health Effects. National Center for Biotechnology Information (NCBI). Cold-Water Immersion
Metabolic Rate During Cold-Water Immersion. NCBI Bookshelf. Metabolic rate during cold-water immersion
