Yes, having a fever can increase the amount of body fat burned because you are increasing your metabolism during the process of your body responding to the pyrogen.
A pyrogen is a substance that causes fever and can consist of a bacteria, virus, or even a reaction to a substance or medication.
When you have a fever, your body is working hard to fight off the invader and this causes your metabolism to increase.
This will result in your body utilizing (burning) more calories than usual and some of those calories will be coming from stored body fat if you are in a caloric deficit by eating less when you’re febrile.
What Happens to My Body During a Fever?
A fever is a response by the body to an infection or other illness. In order to fight the invader, the body must raise its internal temperature which is the body’s attempt to fight it.
This is done by releasing substances such as cytokines and prostaglandins, which signals the hypothalamus to raise the body’s set temperature point. This is all part of a response by our immune system which also will release a variety of other bodily chemicals in the process.
The hypothalamus is the part of our brain that regulates our body temperature, and it plays an important role in a fever. In response to an infection, the hypothalamus will reset our internal body temperature to a higher number.
There are many conflicting normal ranges for body temperature, but according to Cleveland Clinic, a fever is considered having a temperature greater than 100.4F. The average normal body temperature is 98.6F.
This entire process may cause us to feel awful and alternate between feeling extremely hot and then cold very quickly. This will cause us to shiver while also raising our metabolic rate.
Metabolism is Responsible for Fat Burn in Fever
The metabolism plays a very important role in losing weight, and it is the reason why we will burn an increased amount of calories which leads to the burning of body fat when we have a fever.
Check out this clinical study that was carried out on a sample of 362 patients.
The following results showed important changes in the following organ systems during a febrile state:
Increased heart rate in 53 of the total number of patients.
Increased respiratory rate in 69 of the total number of patients.
Altered GI tract in 71 patients.
Changes in renal function in 55 patients which included decreased urinary output.
This shows how having a fever is able to increase metabolic activity within the body. When we increase our metabolic activity, this requires additional calories to do so.
The body will then burn stored fat if burning the additional calories puts us into a calorie deficit, and this is how having a fever can help cause you to burn fat.
Most people when they are ill are not overeating and may not have as big of an appetite, so naturally you are more likely to eat less.
How Many Additional Calories Does a Fever Burn?
It is estimated that a moderate fever can burn anywhere from 100-500 additional calories per day. The number of additional calories burned during a fever will depend on how high the fever is, how long it lasts, and the age and weight of the person.
A more severe or higher fever could potentially burn even more as for every degree your body temperature rises, the body’s metabolism is thought to rise by 7%.
For example, if you have a body temperature of 102°F and your normal temperature is 98.0°F, then your metabolism has increased by approximately 30-32%.
If you weigh 150 pounds and your BMR (basal metabolic rate) is 1400 calories per day, then a 30% increase in metabolism would mean you are burning an extra 420 calories per day.
Should I Still Maintain My Calorie Deficit when I have a Fever?
You do not have to remain in a calorie deficit when you are sick with a fever, you can stay around maintenance. However, I do not recommend going into a calorie surplus.
It is more important to focus on getting rest, staying hydrated, and allowing your body to heal. You can always get back on track with focusing on your calorie deficit when you are feeling better.
This also means that you should not use this time to overeat. Yes, you will be burning more calories, but that does not give you a free pass to eat whatever you want and it having zero effect on weight gain.
It is still possible to gain an increased amount of weight or undo your progress if you overeat in a calorie surplus when sick, this is why the best idea is to just stay at your maintenance value of calories.
Make Sure you Eat and Drink
You want to continue to eat and drink plenty of fluids when you have a fever. Don’t utilize having a fever or being sick as a weight loss tool. It is not worth it to lose weight if you are putting your health at risk.
Some important things to eat and drink when you have a fever are:
Water: Staying hydrated is crucial when you have a fever. You can become dehydrated quickly, and this will only make your symptoms worse. Drink plenty of fluids, and if you are having trouble keeping them down, try drinking small amounts often or sucking on ice chips.
Broth: This will help you stay hydrated while also giving you some electrolytes and nutrients. Avoid anything that is greasy or high in fat as this can make nausea worse.
Fruit juice: This can help increase your fluid intake while also giving you some vitamins and carbohydrates. Try to avoid sugary juices and opt for 100% fruit juice instead.
Sports drinks: These can help restore electrolytes that are lost through sweating.
Jell-O: This can help with hydration and is a good option if you are having trouble keeping fluids down.
High protein snacks and meals: Protein is essential for healing. Try to include foods like eggs, chicken if you can keep them down.
Do Fevers Burn Muscle?
It is possible to burn muscle in a fever without intending to. It depends on how high your fever is and how much protein you are consuming during the time you are febrile or sick.
There are studies that suggest that during a fever, the body turns to protein catabolism instead of glucose. This switch over means that muscle is being used as an energy source during this time because protein is more readily available.
The body will first use amino acids from dietary protein and then turn to muscle tissue if more protein is needed. This can lead to muscle wasting, which is why it’s important to consume enough protein when you’re sick.
Elevated temperature has been proposed to contribute to accelerated muscle protein degradation during fever and sepsis in this study. Of course, this study utilized rats and not human but the research is there.
To prevent muscle loss during a fever, make sure you’re consuming enough protein. This can be difficult if you’re not feeling well, so consider drinking a protein shake or eating high protein foods such as eggs, chicken, or fish.
You can also choose to get some extra protein through a protein supplement. Remember, protein is always important to include, not just when you’re sick!
Last Words
Having a fever can increase the amount of body fat you burn by increasing metabolic response.
It is important to focus on getting rest, staying hydrated, and allowing your body to get back to normal. Don’t focus too much on your calorie deficit when you feel too sick. You can always get back on track with focusing on your calorie deficit when you are feeling better.
Make sure you continue to eat and drink plenty of fluids when you have a fever as well as getting in adequate protein to protect from muscle breakdown.
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