Does a cold shower or ice bath burn a lot of calories?

Not many. Short cold exposure raises energy expenditure while it lasts, and a meta-analysis of mild cold (16 to 19°C) found about 188 extra calories over a full day. A 5 minute shower is a tiny fraction of that. Shivering in cold water can push metabolic rate 2 to 5 times above resting, but only for the minutes you stay in.

Is it better to exercise in the heat or the cold to burn fat?

The workout itself burns the calories, and the weather changes that number only a little. Walking with a load at 37°C raised oxygen uptake and energy expenditure compared with 20°C in one study, but heat also cuts your capacity and raises injury risk. Pick the conditions you can sustain safely and consistently.

Does sleeping in a cold room help you lose weight?

In the NIH ICEMAN study, five men who slept at 19°C for a month grew their brown fat by about 42 percent and burned more calories after meals. The study did not measure weight loss, and the effect reversed after a month at 27°C. A cool bedroom is a reasonable habit, not a weight loss plan.

Why do I weigh less after a sweaty workout?

That is water. People routinely sweat about 1 liter an hour in hot conditions, and 1 liter of sweat weighs about 1 kilogram. The weight comes back when you drink. Sweating is a cooling system, not a fat burning system.

Do people who live in cold climates burn more calories all year?

Field data say yes, but mostly because of activity, not the cold alone. Outdoor course students in cold climates burned about 1,550 more calories a day than in temperate ones, from hard physical work plus keeping warm. Soldiers on cold weather operations reach 3,400 to 6,155 calories a day, driven by snow travel and heavy gear.

Do You Burn More Calories in Cold Weather or Hot Weather?

The short answer: Cold weather burns more calories than hot weather, but the margin is small. A 2022 meta-analysis of 10 trials found that mild cold (16 to 19°C) raised energy expenditure by about 188 calories a day compared with 24°C. Hot weather adds almost nothing at rest, and sweating itself does not burn fat. In real life, clothing, heated rooms, and body fat erase most of the cold effect, so exercise matters far more than the forecast.

How does your body burn calories to stay warm?

Your body holds its core near 37°C. When skin cools, it spends energy to make heat. It has three main tools.

Shivering. Muscles contract without doing useful work, and almost all of that energy becomes heat. The Institute of Medicine review Physiology of Cold Exposure reports that metabolic rate "can increase two- to fivefold" during shivering. Young men resting in 5°C air with a light wind used about 15 percent of their maximal oxygen uptake just to stay warm.
Non-shivering thermogenesis. Muscle and other tissues raise their heat output without visible shaking. This is the main response to mild cold indoors.
Brown adipose tissue (BAT). Brown fat burns glucose and fatty acids directly as heat. A 2009 New England Journal of Medicine study found active brown fat in 23 of 24 healthy men at 16°C, and in none of them at 22°C.

Heat works the other way. Blood shifts to the skin and sweat evaporates. Both are cooling systems, and neither costs much energy on its own.

How many extra calories does cold exposure burn?

The best pooled estimate comes from a 2022 systematic review and meta-analysis in Frontiers in Physiology. Across 10 randomized trials, acute exposure at 16 to 19°C raised energy expenditure by a mean of 188 calories a day (95% CI 140 to 237) versus 24°C. Exposures ran from 30 minutes to 12 hours and stayed just above each person's shivering point.

Individual studies land in the same range or lower:

An NIH study of 24 adults moved people from 24°C to 19°C in light clothing. Energy expenditure rose 5.3 percent on average. Women responded more than men, 9.1 percent versus 2.3 percent.
In the 2014 Diabetes study by Chondronikola and colleagues, 5 to 8 hours of cooling vests at about 19°C raised resting energy expenditure by 15 percent. That gain appeared only in the seven men with active brown fat. The five men without it showed no significant change.
The 2009 NEJM study found brown fat activity was significantly lower in overweight and obese men. The 2022 meta-analysis notes that "no increase in EE was observed in obese individuals" after short acute cold.

So the honest answer for a lightly dressed adult in a cool room is roughly 100 to 200 extra calories a day. Our guide to calories burned walking 10,000 steps shows how quickly activity beats weather.

Does brown fat make a real difference?

In the NIH ICEMAN study, Lee and colleagues had five men sleep at least 10 hours a night in a climate controlled room for four months: 24°C, then 19°C, then 24°C, then 27°C. After the 19°C month, brown fat volume rose by 42 percent and diet-induced thermogenesis rose by 32 percent. After the 27°C month, brown fat fell to 18 percent below baseline. The authors wrote that "the blunting of BAT function due to widespread use of indoor climate control could be a neglected contribution to the obesity epidemic."

Brown fat also has metabolic effects. A 2015 Nature Medicine study gave eight people with type 2 diabetes 10 days of cold acclimation at 14 to 15°C. Peripheral insulin sensitivity improved by about 43 percent, but brown fat glucose uptake rose only slightly. Most of the benefit came from skeletal muscle.

The calorie math is the sobering part. A 2024 review in the Journal of Clinical Investigation modeled mild cold exposure at three brown fat volumes. At 150 mL, brown fat burned about 12 calories a day. At 550 mL, about 46. Only at an unusual 2,550 mL did it reach 211 calories a day. The authors add that brown fat clears less than 1 percent of circulating glucose and fatty acids. Muscle, through shivering and non-shivering activity, does most of the work in the cold.

Does hot weather or sweating burn calories?

At rest, no. In a field study by Ocobock (2016), 59 outdoor course students spent a month each in different climates. Total energy expenditure was statistically the same in hot and temperate conditions (p = .97). Cold climates added about 1,550 calories a day, from hard physical activity plus the cost of staying warm.

Sweat is water, not fat. The Institute of Medicine review Physiological Responses to Exercise in the Heat notes that people "routinely have sweating rates of 1 liter per hour" during hot work. Every liter you lose comes back with the next drink. The scale drop after a hot workout is fluid, not fat.

Exercise in the heat is the one place heat adds calories. In a 2024 Army Research Institute of Environmental Medicine study, 10 men walked for 90 minutes with a pack at 30 percent of body weight. Oxygen uptake and energy expenditure were higher at 37°C than at 20°C, and the body burned more carbohydrate. The same IOM review found total metabolic rate rises with ambient temperature during submaximal exercise. Two catches: maximal oxygen uptake was 0.25 liters a minute lower at 49°C than at 20°C, and heat acclimatization then cut submaximal oxygen uptake by 14 to 17 percent for stair stepping. The CDC's NIOSH guidance puts full heat acclimatization at 7 to 14 days.

Why do clothing and heating shrink the difference?

Every cold study above used light clothing and a controlled room. The ICEMAN participants wore hospital scrubs with an insulation value of 0.4 clo. Real winter looks different. The IOM cold review states that people who "wear clothing, remain in shelters" reduce their physiological strain, and that subcutaneous fat provides "significant insulation against heat loss." A coat, a heated car, and a 21°C office keep your skin near thermoneutral.

Activity blunts it too. Ocobock found that physical activity reduces thermoregulatory costs in cold climates but increases them in hot ones. Working muscle makes its own heat, so a brisk walk in the cold replaces shivering rather than adding to it.

The large cold weather numbers you may have seen come from terrain and gear, not temperature. A 2024 Journal of Applied Physiology review of military cold operations reports 3,400 to 6,155 calories a day. Walking in snow with 10 cm of sinkage costs about 2.84 times normal walking, and tactical boots add 7 to 10 percent.

What should you do with this if you want to lose weight?

Treat weather as a rounding error. A cool room may add 100 to 200 calories a day if you stay lightly dressed for hours. Neither season replaces a real deficit. Start by finding your baseline with our guide on how to calculate TDEE, then build the gap with food and movement. If tracking feels like too much, our article on a calorie deficit without counting covers simpler methods.

Two practical notes:

If you always feel cold, gain weight easily, or tire quickly, ask your clinician about thyroid function. The thyroid sets your resting metabolic rate, and thyroid.md explains how low thyroid output changes heat tolerance and weight.
Do not chase sweat. The CDC warns that in air above 90°F a fan can raise body temperature, and lists unusually heavy sweating as a warning sign of heat illness.

The bottom line

Cold beats heat, but not by much. Lab studies at 16 to 19°C show about 188 extra calories a day, most of it from muscle rather than brown fat. Brown fat at normal volumes burns only 12 to 46 calories a day. Hot weather adds nothing at rest, and sweat is water. Clothing, heating, and body fat cancel most of the cold effect, while exercise burns far more than either season. Dress for comfort, move every day, and manage the deficit on your plate.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your clinician before starting cold exposure or hot weather exercise, especially if you have heart disease, diabetes, or a thyroid condition.