Does The Body Burn More Calories When Sick?

a lady on her sick bed

Calories are the units of energy that your body uses to function. Even when you are resting, your body needs energy to keep your organs working, your heart beating, and your lungs breathing. This is known as your resting metabolic rate (RMR). It’s like the energy your body spends just to keep the lights on in an empty room.

Now the question is, does the body burn more calories when sick? Yes, the higher body temperature that comes with sickness can make you burn more calories. You can burn 7–10% more calories for every 0.5–1°C or 1°F rise in body temperature.

How does your body burn calories when you are sick?

When you become sick, your body may develop a fever as part of its natural defense against invading disease-causing microorganisms. Fever is essentially when your body temperature rises significantly above the usual 37°C.

Research has shown that for every one-degree increase in fever, your body’s energy expenditure goes up by about 10%. This heightened energy expenditure means that your body requires more fuel, typically in the form of calories.

However, if you find yourself not wanting to eat when you’re sick, your body might resort to using its stored energy reserves, such as fat or muscle mass, as a source of fuel.

Several studies involving adults have documented weight loss as a consequence of fevers resulting from various illnesses.

Does the body burn more calories with a cold?

Now, what happens when you catch a cold without experiencing a fever? Does your body still burn more calories in this situation? The available data on this topic is somewhat limited, but here’s what we know.

The primary reason for burning extra calories during a fever is the effort your body puts into raising its temperature, a response that doesn’t occur with a common cold. However, there are other factors that can influence your calorie balance when you have a cold.

Firstly, a cold often affects your appetite. If you only eat when you’re hungry and feel like it, you might end up consuming fewer calories while you’re unwell. This can sometimes result in temporary weight loss during a cold.

Additionally, there could be a modest increase in calorie expenditure to combat the infection even without a fever. While this increase is not as significant as when you have a fever, there is still some extra work going on within your body, such as the multiplication of white blood cells, which does consume some calories.

Does being sick make you lose weight?

lose weight

It’s a common occurrence to experience at least temporary weight loss when you’re unwell.

The weight you shed during sickness is primarily water weight, which tends to come back once you’ve recovered. However, there’s a possibility of losing actual body fat or muscle if you’re consuming significantly fewer calories than usual and/or running a high fever.

When people are sick, they often eat less. This reduction in food intake can lead to having less food in your body and depleted glycogen stores (the stored carbohydrates in your muscles), both of which contribute to a drop in weight.

Illness can also lead to dehydration, especially if you’re not diligent about drinking plenty of fluids and replenishing your electrolytes. This can further lead to a loss of water weight.

In more severe cases, if you consistently maintain a significant caloric deficit over an extended period, you could potentially burn fat or muscle. However, during short-term illnesses, especially if you’re eating an adequate amount of food, significant muscle or fat loss is unlikely.

It’s important to remember the increased calorie requirements during a fever, as discussed earlier. To prevent the loss of fat or muscle during a fever, it’s advisable to consume a little extra to cover the additional energy your body needs to cope with the fever.

Should you eat more when you are sick?

eat when you are sick

When you’re sick, you should eat to support your recovery. It’s not about eating more, but eating the right foods to provide your body with the nutrients it needs to fight off the illness and recover. Below are some guidelines for eating when you are sick.

  • Hydrate: Drink lots of water, herbal tea, and clear broths to stay hydrated.
  • Nutrient Boost: Eat foods rich in vitamins and minerals like fruits, vegetables, lean proteins, and whole grains.
  • Cut sugar: Avoid sugary stuff because it can weaken your immune system.
  • Listen to Your Body: If you’re not too hungry, have smaller, more frequent meals.
  • Comfort Foods: Enjoy comforting dishes like chicken soup, but don’t overdo it.
  • No Alcohol or Caffeine: Skip alcohol and caffeine, as they can dehydrate you.
  • Seek Advice: If you’re very sick, talk to a doctor for guidance on your diet and recovery.


In conclusion, while there is an increase in calorie expenditure when you are sick, it is not a substantial amount. Your body does not burn a significantly higher number of calories when you are sick.


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