New study uncovers a surprising effect of cold-water immersion

Spending half an hour submerged in cold water could lead people to eat more in the hours that follow, according to a new study published in Physiology & Behavior. The research showed that participants consumed significantly more food after a session of cold-water immersion compared to when they sat in warm water or just sat in a room at a comfortable temperature. This finding may be important for people using cold-water exposure to support recovery, improve well-being, or manage weight.

Cold-water immersion, or sitting in cold water for therapeutic or recreational purposes, is growing in popularity. Many athletes and fitness enthusiasts use it to reduce muscle soreness after exercise. Some people also use it as a way to boost mood or improve overall health. But as more people adopt cold-water immersion, researchers have started to question whether it could influence other behaviors—especially eating.

Because the body loses heat more quickly in water than in air, and has to work harder to stay warm, cold-water exposure may increase energy expenditure. Some studies suggest this may also increase appetite or lead to overeating afterward. Until now, it remained unclear whether cold-water exposure alone, without any exercise involved, affects food intake.

To explore this question, a team of researchers in the United Kingdom designed an experiment to isolate the effects of passive cold-water immersion. They recruited 15 healthy and physically active adults—10 men and 5 women—between the ages of 20 and 59. The participants were not dieting, did not smoke, and had been weight-stable for at least three months. To avoid bias, they were told the study was about how water immersion affects energy expenditure, not appetite or eating behavior.

Each participant completed three different trial conditions in random order, with at least a week between each one. In one condition, they sat chest-deep in 16°C (about 61°F) water for 30 minutes. In another, they sat in warmer water at 35°C (95°F), a temperature considered thermoneutral for water. In the third condition, they sat in a room set to 26°C (79°F) air, also considered thermoneutral. In all three trials, participants were immersed or seated at the same time of day and followed the same pre-immersion routine, including a standard breakfast.

Throughout the immersion sessions, the researchers measured energy expenditure using indirect calorimetry and monitored core body temperature, shivering, heart rate, and subjective feelings of hunger and fullness. After each session, participants were dried off and presented with a homogenous pasta meal. They were instructed to eat until they felt “comfortably full.” The researchers then weighed how much food was eaten and calculated total energy intake.

The results revealed a clear pattern. After sitting in the cold water, participants ate significantly more food. On average, they consumed about 2,783 kilojoules (kJ), compared to 1,817 kJ after the warm-water condition and 1,894 kJ after the thermoneutral air condition. The increase in energy intake after cold-water immersion was about 34% higher than after warm-water immersion and 32% higher than after the air-based condition. These differences were statistically significant and observed across participants, regardless of their body size or composition.

Importantly, participants did not report feeling hungrier after the cold-water session, nor did they rate their levels of fullness or satisfaction any differently across the three conditions. This suggests that their increased eating was not driven by subjective feelings of appetite but may have been a physiological response to the cold exposure itself.

The researchers also found that energy expenditure was higher during the cold-water immersion. Participants burned approximately 224 kJ during the 30-minute cold session, compared to about 135 kJ in the warm water and 129 kJ in the thermoneutral air. Shivering, which was absent in the warm conditions, was commonly reported during cold-water immersion and ranged from mild to severe.

A drop in core body temperature was also observed after the cold exposure. Although body temperature remained stable during the 30-minute immersion, it fell significantly in the 15 minutes afterward—an effect known as the “after-drop.” This delayed drop in core temperature may reflect the body’s internal redistribution of cold blood from the skin back into the core. The researchers propose that this cooling effect may trigger an increase in food intake, possibly as a way to generate heat through digestion.

While the study cannot say for certain why people ate more after cold-water immersion, the findings suggest that the body may be attempting to restore thermal balance by taking in more energy. One possible explanation is that the body uses food as a fuel source to warm itself up, through what is known as the thermic effect of food. This is the increase in energy expenditure that occurs during digestion. The researchers speculate that the extra calories consumed may help raise body temperature after cold exposure, although more research is needed to confirm this.

Interestingly, the researchers also found that food intake was not higher after warm-water immersion, suggesting that being in water alone was not enough to trigger extra eating. Nor was there a significant difference between the warm-water and thermoneutral air conditions. This contradicts some earlier research that found increased energy intake after both warm and cold water immersion following exercise. However, in the present study, participants were not physically active before their immersion sessions, and body temperature was measured using more accurate methods.

The findings raise new questions about how environmental temperature, body temperature, and eating behavior interact. Some animal studies have shown that specific brain regions involved in hunger are activated by cold exposure. For example, in mice, neurons in the hypothalamus become more active in the cold and drive food-seeking behavior. While this has not yet been directly tested in humans, the current study lends support to the idea that cold exposure may stimulate eating even in the absence of conscious hunger.

But, as with all research, there are limitations to keep in mind. The study looked only at short-term effects and did not measure what participants ate for the rest of the day. It is possible that people naturally adjust their intake later on to compensate for the extra calories consumed. The study also included a relatively small sample of 15 participants, though the authors note that this was sufficient to detect meaningful differences in energy intake. Another limitation is that hormone levels were not measured, so it remains unknown whether changes in appetite-related hormones such as ghrelin or leptin played a role.

Despite these limitations, the findings could have practical implications. People who use cold-water immersion for recovery or well-being may be at risk of unintentionally increasing their food intake afterward, which could make it harder to manage weight. While cold exposure does increase energy expenditure slightly, the increase in food intake observed in this study outweighed the calories burned during immersion. Whether this effect persists over time or leads to changes in body weight with repeated cold-water use remains to be seen.

The authors encourage future research to explore whether similar effects occur after longer or repeated immersion, how cold exposure affects appetite-regulating hormones, and whether individual differences such as body composition or fitness level influence responses. More studies are also needed to test whether strategies like meal timing or food composition could help offset the tendency to overeat after being in cold water.

The study, “Effects of cold-water immersion on energy expenditure, ad-libitum energy intake and appetite in healthy adults,” was authored by Marie J. Grigg, C. Douglas Thake, Judith E. Allgrove, and David R. Broom.