Calories When Sick (How many do you burn and what to eat) | Millennial Hawk (2023)

Being sick isn’t fun. It always makes me feel weak, fragile, and vulnerable. Today I will explain if your body burns more calories when sick, and what should you eat, based on the research I’ve done on Pubmed, Hindawi, Taylor and Francis, and other peer-reviewed journals and articles.

Calories When Sick (How many do you burn and what to eat) | Millennial Hawk (1)

Do you burn more calories when sick?

It turns out that your body does burn more calories when you’re sick, a new study reveals how.

Leah MacDonald, Ph.D. from La Trobe University in Melbourne, Australia says “calories do matter when you’re sick because the body has to use more calories to be able to combat the sickness and recover faster.”

“Sickness and fever result in increased metabolic heat production, sohaving enough energy increases the chances of fighting off the virus.”

“On the other hand, not enough calories may cause a lack of energy and extends sickness time,” says Dr. MacDonald.

Changes in calorie expenditure when sick

It’s always a challenge to meet nutritional needs when sick.

“During sickness, increased calories and protein must be delivered to support protein synthesis and to maintain the body’s homeostasis,” says Juan Ochoa Gautier, MD, a Medical Director from the intensive care unit in New Jersey.

“The body burns more calories because during sickness the viruses and bacteria dramatically modify cellular metabolism.”

“This starts a cascade of metabolic processes, increases metabolic rate, and elevates core body temperature to fight against the viruses,” explains Dr. Gautier.

How many calories do you lose when sick?

Calories When Sick (How many do you burn and what to eat) | Millennial Hawk (2)

It’s hard to estimate precisely how many calories you lose when you are sick. As of right now, there are no peer-reviewed journals and articles that clarify this information.

We know that sickness can elevate core body temperature. And, some data shows that higher core body temperatures appear to increase metabolism.

Daren Heyland, MD,is a critical care doctor at Kingston General Hospital who has published approximately 300 peer-reviewed papers.

“During sickness, the body elevates its basal metabolic rate by around 5-7% for every half-degree Celcius,” says Dr. Heyland.

Dr. Heyland suggests that for eachdegree Celsius,your body temperature rises, and your metabolism increases by 10 to 13 percent.”

This means you can lose 100 to 200 calories for every 0.5°C increase in core body temperature during sickness.

NOTE: Remember that these numbers are just estimations and should be taken with a grain of salt. There are many other factors that can influence your calorie expenditure like body weight, age, lean muscle mass, and more.

Do you burn more calories when fighting infection?

Infection can happen for a variety of reasons.

Alex Romanyukha, Ph.D., a senior health physicist at Naval Dosimetry Center, says “when bacteria, viruses, yeast, fungi, or other microorganisms spread in the body, you can burn more calories”.

“The body elevates metabolism and initiates the number of metabolic changes that contribute to the maintenance of body homeostasis.”

“Energy is needed to combat germs and bacteria, which is a natural response to illness and infection,” says Dr. Romanyukha.

Do you burn more calories when you have a fever?

Fever is a symptom of having a higher-than-normal body temperature, which can be caused by several factors, according to Mayoclinic.

It triggers the thermoregulatory part of the hypothalamus that increase the core body temperature(above 36.6°C.)

This means that your body can burn more calories when you have a fever. Increased body temperature increases resting metabolic rate and as a result, the body burns more energy.

Of course, apart from body temperature, there are other physiological changes going on like:

  • Metabolic adaptations
  • Sleep/wake cycle changes
  • Hormonal changes

And all of them play a role in your appetite and how the body will use energy.

How many calories does having a fever burn?

According to the article from Johns Hopkins, we can estimate that fever can burn around 20% more calories, compared to a homeostatic state.

During fever, the body increases basal heat production by 20-50 percent. Also, during fever, the body switches energy sources from using glucose to using protein and fat.

Glucose is a great medium for bacterial growth, therefore, the body halts utilizing it.

Do you need more calories when sick?

It turns out that your body does not need more calories when sick, according to a recent study.

Shinobu Yamamoto,Ph.D., a researcher from New York, documented in her recent article that “eating just below calorie maintenance was associated with better outcomes, including shorter hospital stays, ventilator dependence, use of antibiotics, and even mortality.”

“In the contract, inadequate calorie and protein intake during illness was associated with poor clinical outcomes.”

In other words, there is a fine line between eating less and too little. Eating less seems to enhance the body’s immune system, whereas eating too little (especially not enough proteins) during sickness often leads to poor recovery.

Here in the video below, Thomas DeLauer provides some insights about calories you should eat when sick.

Feed a cold, starve a fever

In her recent study on rodents, Dr.MacDonald documented that “25-50 percent calorie restriction was able to suppress sickness.”

“Calorie restriction was documented in the past to alter cytokine levels, but this was the first time to show that calorie intake also matters in sickness.”

According to Dr. MacDonald, “intermittent calorie restriction was able to enhance anti-inflammatory pathways.”

In other words, you do burn more calories when sick because during the period of sickness or infection. The bodyincreases resting metabolic rate and raises oxygen consumption.

It also increases the use of proteins as an energy source and elevates heat production, which all comes with higher calorie burn.

How many calories should you eat when sick?

Getting the right number of calories means you can get a faster recovery and start to feel better.

“You should be getting around 2,000 to 3,000 calories when sick,” says Dr. Heyland.

“Things that influence calorie expenditure will be body weight and lean body weight as heavier people need more energy to increase core body temperature”

“It also depends on things like your physical activity, lean body mass, and the type of food you eat,” says Dr. Heyland.

In other words, it depends.

For me, being sick is a perfect time to focus on a healthy diet. Try adding more protein, including fresh fruits in your meals, or even blend leafy green vegetables with your smoothies.

This may not shorten your sickness, but it can make you feel better.

Should you count calories when sick?

I would not recommend you count calories when you are sick (unless you have an IFBB show coming up). Instead, focus on quality foods.

Remember that the immune system needs plenty of nutrients, so if your diet is poor, you may get sick more often.

Of course, if you’re used to counting calories, that’s fine.

(This may help you control your calorie intake.)

However, if you’re not feeling comfortable and don’t have any weight goals in mind, I recommend avoiding calorie counting.

What to eat when you are sick?

Calories When Sick (How many do you burn and what to eat) | Millennial Hawk (3)

You might not realize it, but what happens in your gut, can play arole in your overall well-being, especially when fighting off the germs. These foods can help you boost your immune system quickly and recover from sickness.


Garlic acts like an antibiotic and can help to combat viruses. Crush 2-3 garlic cloves and add them to your meals. Garlic goes well in tomato and mushroom sauces.

Use a blender, food processor, or palm of your hand to press the blade down onto the clove.


Honey has a lot of antibacterial and antimicrobial properties. Try to find organic honey in your local market.

Honey goes well with tea, milk, or warm water. You can also mix 1-2 scoops into your salad, together with spices and paprika.

Chicken soup

It’s always a good idea to make chicken broth when sick. It can help you stay hydrated, deliver electrolytes and move pathogens out of the body.

The last thing you want during sickness is dehydration.


During inflammation time, glucose isn’t used for energy, therefore, the number of amino acids from dietary proteins needs to be higher than usual.

When you’re sick, include protein-rich sources with each meal like poultry, fish, eggs, and dairy. For men, use two palms of high-protein dense foods, and for women, one palm.

If you don’t feel hungry, you can make a shake or a smoother one with a protein powder.

My favorite protein shakes are from the company Optimum Nutrition.

Calories When Sick (How many do you burn and what to eat) | Millennial Hawk (4)

Vitamins and minerals

Vitamins play a critical role in the strength of the immune system. Ensure your diet is rich in vitamins A, C, D, E, B12, B6, and B9 can prevent depressing the immune system.

Use multivitamins with minerals like magnesium, copper, zinc, and iron to boost and strengthen your immune system.


Eating rich foods with probiotics can help to balance the gut bacteria. I love fermented products like kefir, sauerkraut, miso soup, and pickles. Some people like to have a glass of wine, cheese, and olives. When you choose wine, ensure you have enough water to stay hydrated.

What you should avoid?

Calories When Sick (How many do you burn and what to eat) | Millennial Hawk (5)

Unfortunately, when being sick, some foods can make us feel worse than others. Here are the foods that should be avoided or consumed in moderation when facing an illness or sickness.

Fatty foods

Avoiding high amounts of fatty meals and foods rich in carbohydrates can help you maintain energy levels.

Excess fat consumption during the infection is difficult to break down and hard on your gastrointestinal system.

Sugary drinks

Try to avoid highly-processed fruit juices from the store as these may slightly inflate your immune system.

Instead, focus on water. Squeezing a lemon or grapefruit is also a good idea as these contain natural antioxidants.


Drink coffee in moderation as it can dehydrate the body. Instead, sip water and other calorie-free beverages throughout the day.

Does your appetite change during sickness?

When I was younger I remember joking that when I was sick, I always lost weight. This was true because when you’re sick, not only you don’t wanna eat, but your metabolism is higher so you burn extra calories.

Let’s face it, being sick can affect your appetite. At that time, some people may notice an increase in appetite, whereas others may feel like their appetite has lowered.

  • From the theoretical perspective, during sickness bacterial infections increase the pro-inflammatory cytokines that increase metabolic rate. (So we should be getting more hungry.)
  • From the evidence perspective, the suppression of appetite during sickness is more common.

According to the article from the International Journal of Epidemiology, “upper respiratory infections, diarrhea, and fevers can suppress appetite and food intake by 15-20%. Some of the illnesses like measles, mumps, or rubella can suppress appetite even more.”

How does it work?

“During the inflammatory response of fever, headache, myalgia, and malaise, the TNF cytokine starts long-term immune reactions that create changes in appetite and energy intake,” says Viktor Peny, Ph.D., an infectious disease expert from Lund University in Sweden.

“The immune system takes up a lot of energy to combat infectious diseases. So halting digestion, suppressing appetite, and moving all the resources to the battle seems like a logical move.”

“Nevertheless, eating nutritious food during times of sickness can add many benefits and speed up the recovery process,” says Dr. Peny.

How to eat when you are sick (and have no appetite)

There are 4 ways to eat when you are sick and have no appetite:

Choose foods that you like

Start by choosing your favorite meals. This is not the time to diet or be in a calorie deficit. Also, tell people around you what you like.

Eat small and often

Small and often means you want to graze throughout the day. If a cooked meal seems like a challenge, have yogurt or cereals.

Eat snacks

Snacking during the day may be helpful. A nice variety of snacks can improve your sensory-specific satiety.

This means the more variety we have, the more appetite we get. My favorite snack that is packed with proteins is Jack Links.

Try smoothies

Having a smoothie is a great choice because it can be delicious, nutritious, and easy to eat.

Being creative and adding some fruits, milk, dark chocolate, and nuts can make your meal a really exciting part of the day.

Try to avoid ready-to-eat smoothies with plenty of simple sugars.

Should you still diet when sick?

I notice that when I’m sick, being in a calorie deficit usually slows down my recovery process. Therefore, I try to stay away from dieting when sick.

Lack of appetite during sickness, poor absorption, loss of water, increased metabolic rate and increased body temperature – all increase the demand for nutrients.

Plus, not eating enough calories can trigger a host of metabolic adaptations, and without sufficient nutrients, the body doesn’t recover well.

“During low-calorie intake, immune system defense mechanisms are weaker and defense against pathogens can be sub-optimal,” says Dr. MacDonald.

For me, one of the things that help is reducing carbohydrates.

My thoughts

The main caveat of the aforementioned scientific papers about calorie restriction, immunity, and infections (at least some of them) is that majority of research is done on rodents in a laboratory setting.

So in reality, we don’t know for sure how sickness can alter our metabolism, calorie expenditure, and nutritional needs.

Everything should be person-centered and investigated based on each individual.

Reducing too many calories and not having enough essential micro and macronutrients can lead to poor recovery and can compromise combating the sickness.

Lessons learned

Being sick is not fun. And depending on what you have, your body will burn slightly more calories at rest, compared to the normal state.

But this shouldn’t be the motivating factor to lose weight. When sick, you should focus on improving your strength by adding plenty of protein-rich foods, whole foods, and even some supplements, if necessary.

The best thing to eat when sick are foods that are high in protein and anti-inflammatory compounds like ginger, curcumin, and garlic.

Don’t forget to drink plenty of water and soups that are high in electrolytes help to stay hydrated.


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