Does Being Sick Cause You To Burn More Calories?

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Having a fever does burn calories, but not by much. An average man would lose about 300 to 400 calories a day if they were sick and stayed in bed all day. A healthy diet and rest can do wonders in making sure that the hard-earned muscle you gained isn’t all wasted because you caught the flu.

Have you ever had one of those months where you’ve been hitting the gym, eating healthy, and noticed your body responds well?

You’ve gained muscle and feel better, but then you suddenly fall sick. Within a couple of days, all your hard-earned muscle seems to disappear. When you look at yourself in the mirror, you look like you’ve lost weight and not the good kind.

There are many reasons that this could have happened. After all, being sick isn’t exactly good for you. But could it be because being sick causes you to burn calories?

If so, how many calories do you burn by being sick? And why? Should you try and eat more when you’re sick?

Or will it be better to fast, especially since you lose your appetite? Is it okay to work out when you’re sick?

What happens to your body when you get sick?

A young man is sick and laying down on the sofa, holding his head because of a headache.

To find out if and why you lose calories when you fall ill, we must first understand what happens to our body when we fall sick.

Whenever you become sick, your immune system creates antibodies and white blood cells to fight the illness. It also protects you from getting the illness again, depending on the illness.

🦠 Whenever a virus or some foreign entity enters your body, your immune system releases inflammatory chemicals to increase your body temperature. This is your body trying to cook the invaders to death.

But raising your body temperature comes with a price. If you’ve noticed that you’ve lost weight during sickness, the below points may be the reason why.

  1. Burning calories – Fighting disease can be tough on your body. Burning calories is one way for your body to get the required energy to fight back and raise body temperature.
  2. Eating less – Your body doesn’t have much time to spend on digestion when it’s fighting a disease. Because of this, when you get sick, you usually lose your appetite. And while you must eat to have energy, sometimes it is just hard to eat, especially if you’re nauseous.
  3. Eating light food – Even when you eat when sick, it will probably not be greasy or oily food that will be hard for your body to digest. This can contribute to your weight loss when you’re sick.
  4. Losing water weight – You might be sweating, vomiting, or making more trips to the bathroom than usual. A lot of water in your body may be lost during an illness which is why it’s always a good idea to stay hydrated.

How many calories are burned when you get sick?

The answer may surprise you.

The truth is that you don’t burn a lot more. Yes, a fever does burn more calories, but so does pumping blood to your organs, eating, or even breathing.

Any activity increases the amount of energy you have to use which then burns calories.

📌 While the exact amount of calories burnt can depend on a lot of different factors, it has been proven that you burn about 7% more calories for each half-degree Celsius increase in fever.

An average 25-year-old would burn about 1650 calories a day if they did absolutely nothing all day.

No walking or standing up, and you’d still burn 1650 calories simply by just existing.

A standard fever would be about 101.3 degrees Fahrenheit, meaning that an average fever would burn about 344 calories per day.

But you’ll also move a lot less when you’re sick, meaning overall, you’d probably burn fewer calories from being active.

The below factors can also help impact exactly how many calories you burn by just falling sick and running a fever

  1. Your body size – If you’re a smaller person, the number of calories burnt would also be less. When you’re bigger, you need more energy to increase your body’s warmth. This means more calories spent.
  2. Your gender – If you’re a woman, it’s statistically more likely that your metabolic rate is a bit lower than a man of the same size. Meaning it takes lesser calories to keep you warm.
  3. Your temperature – Somewhat of an obvious point, but your temperature has a direct impact on the calories spent to maintain it. The higher the fever, the more calories are burnt.

From what we’ve read above, it’s clear that fever plays a key role in burning calories. So what happens when you catch a cold with no fever?

Do you need more calories when sick?

Given that there isn’t an increase in body temperature when you’re having a cold, it makes sense that there isn’t a noticeable increase in calories spent.

There might be a small increase in calories spent to fight the cold, but there isn’t much evidence or data to support this fact.

But here are some simple food you can eat that not only are easy to digest but can also help in getting some calories into your body.

A variety of fruits are shown, which are ideal to eat when you're sick for calories as well as healthy nutrients.
  1. Soup – Personally, some chicken or mushroom soup would be my favorite. But any soup should rehydrate you and get some healthy nutrients into your tummy.
  2. Mangoes and Bananas – Easy to find and eat, these nutritious fruits can help you recover from your sickness faster, depending on how severe it is.
  3. Nuts – A quickly digestible source of healthy fat.

Eating these can help you keep your weight and even recover sooner.

Below are some frequently asked questions you might have about being sick.


Does vomiting burn calories?

Vomiting specifically doesn’t burn any calories, but if you do vomit what you ate, then you will be getting rid of some of the calories you ate.

But even if you do vomit within a few minutes of eating, your body will still have absorbed some calories.

Can you work out when sick?

While a very light exercise wouldn’t do you much harm, it’s generally recommended to take your rest and recover as the last thing your body needs when fighting a disease is another problem to worry about.

Does a fever burn fat?

Yes, it does, but it also burns muscle.

A fever rarely discriminates between fat and muscle but, in general, tends to burn muscle more than fat.


While you do burn calories when sick, you’re also more idle during this time, and your calorie expenditure doesn’t increase drastically.

So, in conclusion, your body does not burn a lot more calories when you are sick.

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Kavisha Rodrigo
I'm a sports person that enjoys researching into pushing the limitations of the human body. When it comes to health, I'm a big fan of working out and staying healthy. For hobbies, I'm a big fan of Pokemon and Coldplay.

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