Cold showers don't directly burn calories, obviously, but there is an indirect causal effect that leads to the burning of calories.
If you read the old blog post Cold Showers Burn Calories we go into the reasons why a little bit, but it is past time that we explain in more detail.
When exposed to cold temperatures, the body triggers thermogenesis, a process in which it generates heat to maintain its core temperature. This thermogenesis can be achieved through two main mechanisms:
Shivering
When the body experiences cold, shivering is one way it generates heat. Shivering involves rapid muscle contractions that generate heat as a byproduct. While shivering may slightly increase calorie expenditure, the overall impact on weight loss is minimal.
Brown fat activation
Cold exposure may activate a type of fat tissue called brown adipose tissue (BAT) or brown fat. Unlike white fat, which stores energy, brown fat is specialized in generating heat through a process called thermogenesis. The activation of brown fat is associated with increased energy expenditure, as it burns calories to produce heat. However, the amount of brown fat in adults is relatively small compared to other tissues, and its overall contribution to calorie burning is not yet fully understood.
The amount of fat/calories that gets burned per shower isn't a lot, although it does vary upon the size of the person, and the cumulative effect of daily cold showers over the course of a year is actually significant.
How many calories are burned?
Honestly, it varies upon the person, how cold the water is, and what methods people use to try and calculate the amount of calories burned.
Here's a conservative estimate of how many calories are burned:
The additional calories burned during a 10-minute cold shower for a 100
kg person would range approximately from 20 to 30 calories. So roughly 25 calories.
It isn't a lot, but if the person had daily showers over the course of a year then they would burn roughly 2 to 3 extra pounds of fat per year.
Over a 10 year period that could be a difference of 20 to 30 lbs.
But remember that is a conservative estimate for a person who weighs 100 kg (220 lbs).
There's also an argument that a thin person would actually burn more calories in a cold shower than an overweight person, because they have less body fat to insulate themselves from the cold. So the number of calories being burned could be inversely connected the percentage of body fat a person has.
Thus someone who weighs perhaps 50 kg (110 lbs) with only 12.5% body fat might actually be burning two or more times the amount of fat by having cold showers than someone who weighs 100 kg (and has perhaps 25% body fat or more) because they are more easily made colder due to a comparative lack of insulation. Thus people who are already thin could potentially prevent themselves from gaining weight by having cold showers regularly.
But it also means that someone who is losing weight would encounter a case of "increasing caloric burn" as they continue to shed body fat, thus seeing a gradual acceleration of weight loss over the long term.
Conclusions?
Cold Showers + Healthy Diet + Exercise = Pretty much guaranteed to lose a lot of weight quickly, and over the long term see the health benefits. The real trick in that situation is to stay motivated. Not everyone wants to have cold showers ever day, eat healthy all the time, and exercise daily.
So what you really need is cheat days:
That 1 day of the week where you allow yourself (as a treat) to have a hot shower.
A high carbs day where you're allowed to eat as much as you want.
A day of relaxation when you can just chill and don't have to exercise.
Having cheat days, combined with tracking your weight/counting calories, are just two ways to stay motivated and keep going.