Do You Need Extra Calories When Sick?

November 18, 2025 •

4 min read

When you are sick, your metabolism typically accelerates, meaning your body burns more calories as it works harder to fight off an infection. This increased energy demand raises the important question: Do you need extra calories when sick? The answer is often yes, but it depends on the severity of the illness and your appetite.

Quick Summary

Illness increases metabolic rate to support immune function, demanding extra energy. This need is especially true during fever, which can significantly raise calorie burn. Focus on nutrient-dense foods and stay hydrated, as appetite may be low. Adequate fuel prevents muscle breakdown and supports faster recovery.

Key Points

Metabolism accelerates during illness: Your body increases its metabolic rate to support the heightened activity of your immune system, which burns more calories.
Fever significantly increases energy needs: A fever raises your body temperature, which can increase your energy expenditure by 10-13% for every 1°C rise.
Risk of muscle breakdown: Not eating enough when sick can cause your body to break down muscle and protein stores for energy, potentially delaying recovery.
Nutrient-dense foods are vital: Focus on easily digestible foods rich in vitamins (C, A, D) and minerals (zinc) to support a robust immune response.
Hydration is paramount: With symptoms like fever and sweating, staying well-hydrated with water, broths, and electrolyte-rich fluids is essential.

The Science Behind Increased Calorie Needs During Illness

When your body is fighting off an infection, your immune system shifts into high gear. This heightened activity requires a significant amount of energy, which is why your metabolic rate increases. For example, a fever, which is the body's natural response to combat pathogens, raises your core body temperature. For every 1 degree Celsius (about 1.8 degrees Fahrenheit) increase in body temperature, your energy expenditure can rise by 10-13%. Other symptoms, like inflammation, shivering, and a faster heart rate, also contribute to a higher overall calorie burn.

Why Calorie Deprivation is Detrimental

When a person is sick, their appetite often decreases due to discomfort, nausea, or congestion. This can create an energy deficit, especially with increased metabolic demands. If you don't consume enough calories to meet these needs, your body will turn to its stored energy reserves. In cases of significant or prolonged under-eating during illness, a portion of the body's energy can come from breaking down muscle or protein stores, not just fat. This process can lead to muscle loss and a prolonged recovery time, as protein is critical for immune function and healing. Therefore, even if your appetite is low, it's vital to provide your body with consistent, easy-to-digest fuel.

The Importance of Hydration and Nutrient Density

While calories are essential, the source of those calories matters significantly. During illness, the body's need for specific nutrients is also elevated. Vitamins like C, A, and D, as well as minerals such as zinc, are crucial for proper immune function and healing processes. Staying hydrated is arguably just as important as consuming calories, especially with symptoms like fever, sweating, and potential vomiting or diarrhea. Dehydration can impede cellular function and the delivery of nutrients necessary for healing.

Fueling Recovery: A Strategy for When You’re Sick

Instead of forcing yourself to eat large, heavy meals, the best strategy is to consume small, frequent, nutrient-dense meals and snacks throughout the day. This approach helps to meet your body's elevated energy demands without overwhelming your digestive system.

Here are some easily digestible and nutrient-rich options:

Broths and Soups: Warm liquids like chicken soup provide hydration, electrolytes, and protein, and can soothe a sore throat.
Easy-to-Digest Carbs: Options like plain toast, bananas, and white rice can provide energy without causing digestive distress.
Lean Proteins: Scrambled eggs, poached chicken, or fish are excellent sources of protein, which is vital for immune cell production.
Hydrating Fruits and Vegetables: Melons, citrus fruits, and leafy greens are packed with vitamins, minerals, and antioxidants that support immune health.
Probiotic Foods: Yogurt containing probiotics can help maintain a healthy gut microbiome, which is connected to immune function.

Comparison of Calorie Needs: Healthy vs. Sick


Factor	Healthy State	Sick State (e.g., with fever)
Metabolic Rate	Normal basal metabolic rate (BMR) for basic functions and activity.	Elevated, potentially by 10-13% for every 1°C increase in temperature.
Appetite	Generally stable and consistent, driven by hunger cues.	Often suppressed or reduced due to illness symptoms.
Energy Source Priority	Primarily uses energy from dietary intake and fat stores.	Relies on stored energy, with an increased risk of breaking down muscle if intake is low.
Hydration Focus	Important for overall health; needs are usually met with standard intake.	Critical to replenish fluids lost through fever, sweating, vomiting, or diarrhea.
Nutrient Density	Important for daily health and maintenance.	Crucial for boosting the immune system and supporting healing processes.
Dietary Strategy	Varied, balanced meals and snacks.	Small, frequent, easy-to-digest, nutrient-dense foods and liquids.

Conclusion

The notion that you must starve a fever or restrict food while sick is a misconception. In fact, providing your body with adequate calories and nutrients is critical for supporting the immune response and ensuring a faster, more effective recovery. While loss of appetite is common, focusing on small, regular portions of nutrient-dense foods and prioritizing hydration is the recommended approach. Listening to your body's hunger cues while focusing on easily digestible nourishment will give your immune system the fuel it needs to get you back on your feet. For more detailed nutritional guidance during illness, consulting a healthcare provider is always advisable.

Key Takeaways

Yes, you burn extra calories when sick: Your metabolism increases to power your immune system, especially with a fever.
Prioritize nutrient-dense foods: Focus on easily digestible meals and snacks packed with vitamins, minerals, and protein to support healing.
Small, frequent meals are best: If your appetite is low, eating smaller portions regularly is more effective than trying to force large meals.
Hydration is critical: Drinking plenty of fluids like water, broth, and tea helps to prevent dehydration, which can be caused by fever and sweating.
Avoid muscle breakdown: Consuming enough calories prevents your body from breaking down muscle for energy, which can prolong recovery.
Listen to your body's cues: Pay attention to your appetite, but ensure consistent, gentle nourishment to support your body's fight against illness.

Frequently Asked Questions

Yes, when you're sick, your body's metabolism increases as your immune system works harder to fight off the illness, resulting in a higher calorie burn.

Instead of focusing on three large meals, try to eat small, frequent portions of nutrient-dense foods throughout the day. Soups, smoothies, and protein shakes can be easier to consume.

While the old adage says to 'starve a fever,' it's better to eat sensible, nourishing foods if you have an appetite. Your body's calorie needs are elevated during a fever, and eating provides the necessary fuel for your immune system.

Focus on easily digestible foods like broths, scrambled eggs, bananas, rice, and toast. Nutrient-rich options such as chicken soup, fruits high in Vitamin C, and vegetables can also be beneficial.

Protein is crucial for building and repairing tissues, including the cells of your immune system. Adequate protein intake helps prevent muscle breakdown and supports a more effective recovery.

Hydration is extremely important. Illnesses often cause fluid loss through sweating (fever) or other symptoms. Staying hydrated ensures nutrients can be delivered to cells and helps the body function properly.

Not eating enough can lead to an energy deficit, which may cause your body to break down muscle for fuel. This can weaken your immune system and prolong your recovery time.