Do You Burn More Calories When Sick?

do you burn more calories when sick

Being sick refers to experiencing an illness or health condition that affects your well-being and normal functioning. Common symptoms of being sick can include fever, cough, congestion, fatigue, body aches, and digestive disturbances. Being sick isn’t fun. It makes me feel weak, fragile, and vulnerable.

When asking do you burn more calories when sick, we can point to a 2007 study by Eileen R. Gibney from the University of Cambridge, which suggest that an increase in energy expenditure, and thus energy requirements, as a direct result of an increase in basal metabolic rate often seen in sickness and disease.

In this article, we will explore several questions related to being sick and its potential impact on calorie burn. Specifically, we will address whether being sick burns calories, whether the body burns more calories when sick, whether higher calorie intake is needed during illness, and whether fever contributes to calorie burn.

Do You Burn More Calories When Sick?

Yes, human body tends to burn more calories when sick because it requires additional energy to combat the illness and facilitate recovery. A 2011 study conducted by Leah MacDonald, Ph.D., from La Trobe University in Melbourne, Australia, suggests that calories play a significant role during sickness.

The body’s metabolic heat production increases due to illness and fever, and having an adequate calorie intake improves the likelihood of effectively fighting off the virus.

Conversely, insufficient calorie consumption may lead to a lack of energy and potentially prolong the duration of sickness. Therefore, it is important to ensure that you provide your body with enough calories to support its increased energy demands when you are sick.

What Are The Changes In Calorie Expenditure When Sick?

When you’re sick, there are significant changes in calorie expenditure as your body responds to the illness and works to restore its balance. Meeting nutritional needs becomes even more crucial during this time.

According to Juan Ochoa Gautier, MD, a Medical Director from the intensive care unit in New Jersey, increased calorie and protein intake is essential during sickness. This is necessary to support protein synthesis and maintain the body’s overall homeostasis.

Dr. Gautier explains that the presence of viruses and bacteria during sickness leads to dramatic modifications in cellular metabolism. As a result, a cascade of metabolic processes is initiated, which includes an increase in metabolic rate and elevation of core body temperature.

These changes in metabolic activity aim to strengthen the body’s defense mechanisms against the invading pathogens.

The elevation of metabolic rate and the increase in core body temperature play vital roles in combating viruses and bacteria. The higher metabolic rate means that your body burns more calories as it works harder to support immune responses and fight off the illness. The rise in core body temperature is an adaptive response that creates an inhospitable environment for the pathogens, inhibiting their growth and replication.

During sickness, the immune system requires additional energy to mount a strong defense. This energy is utilized in the production of immune cells, antibodies, and other molecules that play a crucial role in fighting off the illness. These heightened energy demands further contribute to the increased calorie expenditure during sickness.

When considering whether being sick burns more calories, it’s important to note that specific changes in calorie expenditure may vary depending on the type and severity of the illness, as well as individual factors.

Proper nutrition, including sufficient calorie and protein intake, is essential to provide the body with the resources it needs to support the immune response, facilitate healing, and maintain overall health during sickness.

How Many Calories Do You Lose When Sick?

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 each degree 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.

Do You Burn More Calories When Fighting Infection?

Yes, when fighting an infection, your body tends to burn more calories. This is because the body increases its metabolism and undergoes various metabolic changes to maintain homeostasis in response to the presence of bacteria, viruses, yeast, fungi, or other microorganisms.

According to Alex Romanyukha, Ph.D., a senior health physicist at the Naval Dosimetry Center, the energy required to combat germs and bacteria is a natural response to illness and infection. These processes and the increased energy demand contribute to the body burning more calories during this time.

Do You Burn More Calories When You Have a Fever?

Yes, when you have a fever, you burn more calories. According to a 1997 study by M Benhariz from Necker-Enfants Malades University Hospital, during the fever, energy expenditure was significantly higher compared to the non-fever.

The study found that there was a 16.2% increase in energy expenditure per degree of fever. This means that for each degree increase in body temperature during a fever, your body burns approximately 16.2% more calories.

Additionally, urinary nitrogen excretion was higher during the febrile phase, suggesting increased protein breakdown. The respiratory quotient, which reflects the fuel source used by the body, did not differ significantly between the febrile and afebrile phases.

These findings indicate that fever, particularly associated with infection or inflammation, contributes to a hypermetabolic state and increased energy expenditure.

Fever refers to 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).

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 Burn More Calories When Having a Headache?

Having a headache alone typically does not significantly increase calorie burn. Calorie expenditure is primarily influenced by factors such as physical activity, metabolic rate, and the body’s energy needs for various physiological processes. Headaches, while uncomfortable, generally do not require a significant increase in energy expenditure.

Do You Burn More Calories When Having a Flu?

Yes, when you have the flu, you may burn more calories compared to when you are healthy. The flu is an illness that can cause fever, inflammation, and increased metabolic activity in the body. These factors can contribute to an increase in energy expenditure, leading to the burning of more calories.

However, the extent of calorie burning during the flu can vary depending on factors such as the severity of the illness, individual metabolism, and the body’s immune response. It’s important to note that the increase in calorie burning during the flu is generally modest and may not significantly impact overall weight loss or gain.

Do Humans Need More Calories When Sick?

The human body’s calorie requirements when sick can vary depending on the individual and the specific illness.

For centuries, people have believed in the saying “Feed a cold, starve a fever,” but it’s actually not true. Both colds and fevers require proper nutrition and hydration to support the immune system. When we’re sick, our bodies need more energy to fight off the illness, so we actually need more calories, not less. 

On the contrary what traditional wisdom suggests, recent research indicates that maintaining a slightly lower calorie intake than usual may be associated with better outcomes during illness.

A 2020 study published in Nutrition and Metabolic Insights suggests that your body does not necessarily require more calories when you are sick. According to Shinobu Yamamoto, Ph.D., a researcher from New York, maintaining a calorie intake just below maintenance levels is associated with better outcomes during illness.

Yamamoto’s study found that individuals who consumed slightly fewer calories during sickness experienced benefits such as shorter hospital stays, reduced reliance on ventilators, decreased use of antibiotics, and even lower mortality rates.

On the other hand, inadequate calorie and protein intake during illness were linked to poor clinical outcomes.

These findings highlight the importance of finding a balance in calorie consumption during sickness. Consuming fewer calories, while still meeting the body’s nutritional needs, appears to enhance the immune system and support recovery.

However, it is crucial to avoid insufficient calorie and protein intake, as this can negatively impact the body’s ability to heal and regain strength.

This video provides some insights about how many calories you should eat when sick.

Yes, your body needs energy to heal and repair itself when you’re sick. By conserving energy and using it for essential functions, your body can focus on fighting the illness and recovering faster. Burning more calories may divert energy away from these crucial processes.

This graph illustrates what happens with your calories needs when you’re sick.

do you burn extra calories when sick
  • Immune System Activation. When you’re sick, your immune system becomes highly active to fight off pathogens and restore health. This immune response requires additional energy in the form of calories to fuel immune cell function and the production of antibodies.
  • Increased Metabolic Rate. Illnesses, particularly fevers, can elevate your metabolic rate. This means your body burns more calories at rest to generate heat and support various physiological processes involved in combating the illness.
  • Tissue Repair and Recovery. Sickness often involves tissue damage or inflammation. Your body needs extra calories to support the repair and regeneration of damaged tissues, as well as to facilitate a speedy recovery.
  • Elevated Energy Demands. Being sick can result in general weakness, fatigue, and increased physical and mental stress. These factors can raise your body’s energy demands, requiring additional calories to meet the increased energy requirements.
  • Maintaining Nutritional Balance. Certain illnesses can disrupt your appetite and alter nutrient absorption and utilization. Consuming sufficient calories ensures that your body receives the necessary nutrients to support immune function, prevent muscle wasting, and maintain overall nutritional balance during sickness.

Do Animals Need More Calories When Sick?

According to a 2011 study published in American Journal of Physiology on rodents suggest that calorie restriction, particularly at 50%, can suppress sickness behavior in mice.

The mice were divided into groups fed ad libitum (unrestricted) or subjected to 25% or 50% calorie restriction for 28 days. On day 29, they were injected with lipopolysaccharide (LPS) to induce sickness.

The results showed that the mice on 50% calorie restriction (CR50%) did not develop fevers, displayed shorter fever duration compared to the controls, and showed no signs of anorexia or reduced cachexia (wasting).

This effect may be attributed to the modulation of proinflammatory and anti-inflammatory pathways. However, this study specifically focused on mice, and further research is needed to determine if similar effects occur in other animal species.

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.

What Foods Should You Eat When You Are Sick?

When you’re sick, the foods you consume can have a significant impact on your well-being and immune system. Here are some recommended foods to help boost your immune system and aid in your recovery.

  • Garlic. Garlic acts as a natural antibiotic and can help combat viruses. Add 2-3 crushed garlic cloves to your meals, such as tomato and mushroom sauces.
  • Honey. Organic honey contains antibacterial and antimicrobial properties. Enjoy it in tea, milk, or warm water. You can also incorporate it into your salad with spices and paprika.
  • Chicken soup. Chicken broth is a classic choice when you’re sick. It helps keep you hydrated, provides electrolytes, and aids in removing pathogens from your body.
  • Protein. During times of inflammation, dietary proteins become crucial as glucose is not efficiently utilized for energy. Include protein-rich sources like poultry, fish, eggs, and dairy in each meal. Men should aim for two palms of high-protein foods, while women can opt for one palm. If you don’t have an appetite, consider making a protein shake with powder.
  • Vitamins and minerals. Essential vitamins like A, C, D, E, B12, B6, and B9 play a critical role in strengthening the immune system. Ensure your diet includes foods rich in these vitamins. Consider taking a multivitamin with minerals such as magnesium, copper, zinc, and iron to further support your immune system.
  • Probiotics. Foods rich in probiotics can help balance the gut bacteria, which is beneficial for overall health. Fermented products like kefir, sauerkraut, miso soup, and pickles are excellent sources of probiotics. Some people also enjoy wine, cheese, and olives, but remember to stay hydrated by drinking enough water.

By incorporating these foods into your diet when you’re sick, you can give your body the necessary nutrients to support your immune system and aid in a faster recovery.

What Foods Should You Avoid When Sick?

When you’re sick, certain foods can exacerbate your symptoms and make you feel worse. Here are some foods that should be avoided or consumed in moderation during illness or sickness:

  • Fatty foods. It’s best to steer clear of high-fat meals and foods rich in carbohydrates when you’re sick. Excessive fat consumption can be difficult to digest and put strain on your gastrointestinal system, potentially leaving you feeling even more fatigued.
  • Sugary drinks. Highly processed fruit juices and sugary beverages should be avoided as they can slightly suppress your immune system. Instead, prioritize hydrating yourself with water. You can add a squeeze of lemon or grapefruit to your water, as these citrus fruits contain natural antioxidants.
  • Caffeine. While a cup of coffee can provide a temporary energy boost, it’s important to consume caffeine in moderation when you’re sick. Coffee can dehydrate the body, which is counterproductive when you need to stay hydrated to support your recovery. Opt for water and other calorie-free beverages throughout the day instead.

By avoiding or minimizing the consumption of fatty foods, sugary drinks, and excessive caffeine, you can help your body recover more effectively and manage your symptoms more comfortably during illness. Prioritizing hydration and nutrient-dense foods will support your overall well-being and aid in your recovery process.

Does your appetite change during sickness?

Yes, when we’re sick, it’s common for our appetite to be affected. While some people may experience an increase in appetite, others may notice a decrease.

From a theoretical perspective, bacterial infections during sickness can lead to an increase in pro-inflammatory cytokines, which in turn can raise the metabolic rate. This could potentially make us feel more hungry.

However, evidence suggests that the suppression of appetite is more common during sickness. According to a 1987 study published in the International Journal of Epidemiology, upper respiratory infections, diarrhea, and fevers can reduce appetite and food intake by 15-20%. Certain illnesses like measles, mumps, or rubella can further suppress appetite.

So, while individual experiences may vary, it’s not uncommon to have a decreased appetite during sickness. It’s important to listen to your body and provide it with nourishing foods and fluids to support your recovery, even if your appetite is diminished.

How does your appetite change during sickness?

“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?

When you are sick and experiencing a lack of appetite, there are four effective approaches to ensure you still consume nourishing food:

  1. Opt for foods you enjoy. During this time, prioritize your favorite meals. This is not the moment for restrictive diets or calorie deficits. Additionally, communicate your food preferences to those around you.
  2. Eat small, frequent meals. Grazing throughout the day is beneficial. If consuming a full cooked meal feels daunting, consider opting for yogurt or cereals instead.
  3. Incorporate snacks. Snacking throughout the day can be helpful, as a diverse range of snacks can enhance your sensory-specific satiety. Increasing variety in your snacks can stimulate your appetite. One recommended protein-packed snack option is Jack Links.
  4. Experiment with smoothies. Smoothies are an excellent choice as they can be both delicious and nutritious, while also being easy to consume. Get creative by adding fruits, milk, dark chocolate, and nuts to make your smoothie an exciting part of your day. However, it’s advisable to avoid pre-made smoothies that contain excessive amounts of simple sugars.

Should you still diet when sick?

No, it is generally advisable to avoid dieting when you are sick. Restricting calorie intake during illness can hinder the recovery process. Several factors contribute to this, including decreased appetite, impaired nutrient absorption, water loss, heightened metabolic rate, and elevated body temperature, all of which increase the body’s demand for nutrients.

Insufficient calorie intake can trigger various metabolic adaptations, and without an adequate supply of nutrients, the body’s ability to recover is compromised. Dr. MacDonald emphasizes that during periods of low-calorie intake, the immune system’s defense mechanisms become weaker, leading to suboptimal protection against pathogens.

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.

Should You Count Calories When Sick?

No, you should not count calories when sick. 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.

Michal Sieroslawski

Michal is an exercise physiologist (MSc) and a veteran endurance athlete. He loves to experiment and share his successes and failures to help busy men and women who want to lose weight.

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