Does being cold burn calories?

Maybe you've heard that turning the thermostat down or heading out into the cold can burn fat while you do nothing. It's an appealing idea, especially in winter, when workouts get harder to fit in and the cold costs nothing.

There's real science behind it. Your body works to hold its core temperature near 37°C (98.6°F), and making heat takes energy. Researchers have measured how much in sealed calorimeter rooms, in water-cooled suits and in month-long trials where people slept in cool bedrooms. The numbers are smaller than the headlines suggest, and they show why being cold is a poor stand-in for moving.

Below you'll find how your body responds to cold, how many calories each level of cold burns, what brown fat and shivering actually add, what changes as you get used to the cold, whether cold nights or hot days make a difference, and whether any of it helps you lose weight.

Does Being Cold Burn More Calories?

Yes, once you're cold enough. Your body defends its core temperature in three steps, and only the last two cost much energy:

1. Narrowing the blood vessels in your skin. Your body first cuts blood flow to the skin to keep heat in the core. This costs almost nothing, which is why you can feel chilly without burning extra calories.
2. Non-shivering thermogenesis. If that isn't enough, brown fat and muscle start burning fuel to make heat without any visible movement. This adds a few calories an hour.
3. Shivering. When you get colder still, your muscles contract rapidly and involuntarily. Shivering can multiply your resting energy use several times over.

In their review of the cold research, Castellani and Young (2016) describe the first and last of those steps as the body's main defenses: narrower skin blood vessels cut heat loss, and shivering raises heat production.

The extra burn starts at what researchers call the lower critical temperature, the bottom edge of your comfort zone. For adults in light clothing in NIH chamber studies, it sits at about 21 to 23°C (70 to 73°F). Brychta and colleagues (2019) measured it at 22.9°C in lean young men and 21.1°C in men with obesity. Above that temperature, your body has no need to make extra heat at all.

How Many Calories Does Being Cold Burn?

It depends on how cold you get, and the range is wide. When Brychta and Chen (2017) reviewed two centuries of measurements, reported increases ran from 0 to 280 percent above basal metabolism. The spread came from the temperatures used, how long people stayed cold, how energy was measured and who was tested. The table turns the main lab results into calories.

Read the table in two halves. Without shivering, a cool room adds roughly 5 to 12 calories an hour, about the same as standing instead of sitting, which our post on whether standing burns calories puts at 9 an hour. Water and cooling suits pull heat out of the body much faster than air, so the 80 percent figure needs a strong stimulus that daily life rarely provides. Once shivering starts, the numbers jump into the range of a walk.

Many studies also report the cold burn as a daily rate, such as 300 calories a day. That's what you'd burn if you stayed that cold for 24 hours straight. A 2-hour cold session collects only a twelfth of it.

Brown Fat and Non-Shivering Thermogenesis

Brown fat is the reason cold became a metabolism story. Ordinary white fat stores energy, while brown fat is packed with mitochondria that can burn fuel purely to make heat. PET scans since 2009 have found active brown fat in most healthy adults who are mildly cooled, and the brown fat section of our article on cold shower benefits covers that discovery and what it means for a daily cold shower.

The harder question is how much of the cold burn brown fat supplies. Ouellet and colleagues (2012) used PET tracers to watch brown fat burn fuel in six men during three hours of cooling. Brown fat's own oxidative metabolism switched on, whole-body energy use rose 80 percent, and the men with more active brown fat shivered less. Muscle still matters, though. In Brychta's 2019 study, muscle electrical activity rose in step with the cold burn from the point where extra burning began, so muscle and brown fat work in parallel rather than one after the other.

Body size changes how much room you have to work with. In that study, extra burning in men with obesity started only below about 21°C rather than 23°C, yet their limit of tolerable cold was similar to the lean men's. Their maximum cold burn was well under half as large, about 125 calories a day against 300. The authors pointed to a higher baseline heat output and a similar sensitivity to skin cooling.

Sex makes a smaller difference than most people assume. In a 2024 study of lean young adults, Brychta and colleagues found that women's extra burning started about 1°C lower than men's, at 21.9°C against 22.9°C, mostly because more body fat insulated them. Brown fat activity, muscle activity, the size of the cold burn and how comfortable people felt didn't differ between the sexes.

Does Shivering Burn Calories?

Yes, shivering burns calories quickly, which makes it your body's emergency heater. Each shiver is a burst of muscle contractions that produce heat instead of movement.

In Haman and colleagues (2005), men cooled for 90 minutes at 10°C shivered lightly and produced 2.6 times their resting heat. A second group in a suit circulating 5°C water shivered moderately and reached 3.5 times resting, about 290 watts. That's roughly the energy rate of walking at about 3 mph.

Eyolfson and colleagues (2001) pushed 15 volunteers to their peak. They immersed them in 8°C water until core temperature fell to about 35°C, then warmed the water to 20°C. Peak shivering reached 4.9 times resting metabolism, about 42 percent of their maximal oxygen uptake. For a 72 kg (159 lb) person, that's roughly 7.7 calories a minute in total, about 6 above rest, by our arithmetic from their oxygen figures.

How many calories does shivering burn per minute?

Light to moderate shivering adds about 2 to 3 calories a minute over resting, and the most intense shivering about 6. Per hour, that's roughly 130 to 175 extra calories for light to moderate shivering and 370 at the peak. Peak shivering in that study came with a core temperature near 35°C, the threshold of hypothermia, so it's a warning sign rather than a workout.

Shivering also runs on a different fuel mix from exercise. As shivering moved from light to moderate in Haman's study, carbohydrate's share of the heat rose from 37 to 55 percent, mostly from glycogen stored in the shivering muscles. Fat's share fell from 52 to 37 percent. The authors noted that exercise at a similar energy cost leans far less on carbohydrate.

Shivering may send signals as well. Lee and colleagues (2014) found that cold exposure raised blood levels of irisin, a hormone muscles release during exercise. It rose in proportion to how hard people shivered, by an amount similar to exercise. In lab dishes, irisin pushed human fat cells toward brown-fat-like behavior. Whether that changes body fat in people over time hasn't been shown.

What Happens When You Get Used to the Cold

Repeated cold changes how your body makes heat, and three trials put numbers on it. Two of them, both published in 2013, have their protocols laid out in our review of ice bath benefits. The figures below are the energy side of those studies.

In van der Lans and colleagues (2013), 17 young adults spent up to 6 hours a day at 15 to 16°C (59 to 61°F) in shorts and T-shirts for 10 days. Non-shivering thermogenesis rose from about 11 to 18 percent above resting, and their detectable brown fat volume grew by 37 percent. By the end, they felt more comfortable in the cold and reported less shivering. Their body weight and body composition didn't change.

Yoneshiro and colleagues (2013) gave 12 volunteers with little active brown fat 2 hours a day at 17°C (63°F) for six weeks. Their cold-induced thermogenesis rose from about 108 to 289 calories a day, measured as a daily rate, and their body fat fell by 0.7 kg (1.5 lb), about 5 percent, while a control group's didn't change. Spread over a 2-hour session, that rate comes to roughly 24 extra calories, by our arithmetic. That's far less than the energy in 0.7 kg of fat, and the study didn't report what people ate, so other changes may have played a part.

The most revealing result came from a Canadian team. In Blondin and colleagues (2017), nine men wore a suit circulating 10°C water for 2 hours a day, 5 days a week, for four weeks. The same group had already shown that this kind of program grows brown fat volume by 45 percent. This time, shivering intensity during a cold test fell by 21 percent, yet total heat production stayed the same. Getting used to the cold moved the work from shivering muscle to brown fat without raising the total.

So cold acclimation mostly makes the cold easier to bear. It doesn't turn you into a much bigger calorie burner.

Does Being Cold Burn Calories at Night?

A cool bedroom raises your burn slightly while you sleep, and over weeks it can change your brown fat. In a second 2014 study from the same NIH team, Lee and colleagues had five healthy men sleep at least 10 hours a night in a temperature-controlled research unit for four months, each month at a different setting: 24, 19, 24 and then 27°C (75, 66, 75 and 81°F). They wore light hospital clothes and had only bedsheets. After the cool month, their brown fat volume was 42 percent higher and their insulin sensitivity after meals had improved. The warm month suppressed brown fat again.

Their cold burn didn't change across the four months, though, and neither did their weight: 74.4 kg before the cool month and 74.8 kg after, with fat mass steady at about 14.5 kg. Their desire to eat rose after the cool month. A cool bedroom may help your metabolism in other ways, but it isn't a weight-loss plan. Our page on how many calories you burn sleeping covers what a normal night costs.

Do You Burn More Calories in the Heat or Cold?

At rest, cold wins. Below your lower critical temperature your body has to make extra heat. In warm weather it mostly sheds heat through blood flow to the skin and sweat, and sweating itself takes very little energy. Our review of whether sweating burns calories covers the lab evidence, including an identical yoga session that used the same oxygen in a 35°C room as in a 22°C one.

Does exercising in the heat burn more calories? Not in a way that matters for your weight. Heat raises your heart rate and makes the same pace feel harder, and it often shortens the workout you can manage. Running performance falls as temperatures climb, which our article on whether it's easier to run in the cold or the heat shows with marathon data.

Does Walking in the Cold Burn More Calories?

Usually only a little. A brisk walk makes your muscles produce several times their resting heat, which is often enough to keep you warm without shivering in mild cold. At the same effort, your body does change its fuel. In Gagnon and colleagues (2013), 10 lightly dressed men walked or ran for an hour at 0°C (32°F) and at 22°C (72°F) with their oxygen use held the same. In the cold, about 1.6 more calories a minute came from fat, and their heart rates ran lower.

The extra calories in winter walking come mostly from what you wear and what you walk on. Dorman and Havenith (2009) tested 14 sets of protective work clothing and found that walking, stepping and an obstacle course cost 2.4 to 20.9 percent more than in light clothes. More than half of that extra cost wasn't explained by the clothing's weight, so bulk itself makes moving harder. Snow adds more: walking on it costs more energy than walking on pavement, and the deeper the snow, the more each step costs, as Pandolf and colleagues (1976) measured.

Is Being Cold a Good Way to Lose Weight?

Not on its own. The best trial result so far is 0.7 kg (1.5 lb) of fat lost over six weeks of daily 2-hour cold sessions, and the other trials on this page found no change in weight at all. Cold can also nudge your appetite: the men in the cool-bedroom study wanted to eat more. In a shorter test by Langeveld and colleagues (2016), 2.5 hours at 18°C (64°F) raised energy use without changing hunger or how much people ate at the next meal. The volunteers did find the cold clearly uncomfortable.

Cold plunges and ice baths don't change this picture. They're recovery tools first, and our review of cold plunge recovery research covers what they do for sore muscles and why the timing matters if you lift.

Mild cold sits alongside standing and fidgeting: real, measurable and small. The changes that add up are regular movement, strength training and an eating pattern you can keep. If you want an app to help with the first two, our roundup of the best workout apps for weight loss judges seven options on whether they keep you training and protect your muscle while you lose fat.

Be careful with deliberate cold. The American College of Sports Medicine's position stand on cold-weather exercise, led by Castellani and colleagues (2006), says people with asthma or heart disease can exercise in the cold but should be monitored closely. Shivering that won't stop, numb or white fingers and confusion are signs to get warm right away.

What This Means for You

Being cold does burn calories, and now you know the real size of it: a few calories an hour in a cool room, a few a minute while you shiver, and little change in body weight even after weeks of practice. If you enjoy cold walks or a cooler house, keep them. They get you outdoors, and a cool bedroom may help your blood sugar. Just don't count on the cold to do the work that movement does.

Winter is when routines tend to slip, so make your plan easy to keep. A short strength or cardio session at home counts on the coldest days, and a brisk walk on the milder ones burns far more than standing in the cold ever will. FitCraft's 3D AI coaches lead home workouts with bodyweight and dumbbells, and streaks keep a running count of the days you show up. As Mike, a FitCraft user, put it: “The streak system got me hooked. I didn't want to break my chain.”