Should You Increase Calories When Sick? The Fuel Your Immune System Needs

November 16, 2025 •

4 min read

An age-old adage suggests we should 'feed a cold and starve a fever,' but modern science reveals this advice is only partially correct. The truth is your body needs sufficient energy to fight off any illness, and understanding if and when you should increase calories when sick is key to a speedy recovery.

Quick Summary

The body increases its metabolic rate to fight illness, especially with a fever, so maintaining adequate calorie intake is crucial. Proper nutrition supports the immune system and preserves muscle mass. The type and timing of food are more important than overeating. Stay hydrated and prioritize nutrient-dense, easily digestible options.

Key Points

Metabolism Increases During Illness: Your body burns more calories, especially with a fever, as the immune system works harder to fight off infection, requiring a higher energy intake.
Starving a Fever is a Myth: The outdated saying is harmful, as restricting calories during a fever starves the immune system and can hinder recovery by forcing the body to break down muscle for energy.
Focus on Nutrient-Dense Foods: When appetite is low, prioritize easy-to-digest foods like broths, soups, and smoothies that pack essential vitamins, minerals, and protein.
Hydration is Crucial: Illnesses like fever can cause dehydration, so staying hydrated with water, herbal tea, and electrolyte drinks is a top priority.
Small, Frequent Meals: If a large meal is unappealing, opt for smaller, consistent snacks to provide a steady supply of energy without overwhelming your system.

Do You Burn More Calories When You're Sick?

When you fall ill, your body doesn't shut down; it ramps up its defenses. This increased activity, particularly by the immune system, requires a substantial amount of energy. The body's metabolic rate can increase, especially if you have a fever. For every degree Celsius that your body temperature rises, your energy expenditure can increase by about 10–13%. This is because your immune system works in overdrive, producing immune cells and inflammatory proteins to combat the infection.

Therefore, ignoring your nutritional needs and severely restricting calories can hinder your recovery. A lack of sufficient fuel can force your body to break down muscle protein for energy, a process that can prolong healing and lead to further fatigue. This is why the outdated 'starve a fever' advice is misleading. The focus should be on providing your body with the right fuel, not on avoiding it altogether.

The Problem with Loss of Appetite

One of the most common symptoms of illness is a decreased appetite. Nausea, fatigue, and congestion can make the thought of eating unpleasant. While it's important to listen to your body and not force yourself to eat heavy meals, this doesn't mean you should fast. The goal is to provide consistent, easy-to-digest nourishment. Small, frequent meals or nutritious snacks throughout the day can prevent the body from dipping into its reserves and help you maintain energy levels without overwhelming your system.

Nutrient Priorities During Illness

Your focus shouldn't be on simply hitting a certain calorie count, but on the quality of those calories. The body needs a specific set of nutrients to bolster its defenses.

Fluids and Electrolytes: Dehydration is a major risk, especially with a fever or digestive issues like vomiting or diarrhea. Broths, electrolyte-rich drinks, and herbal teas are excellent choices.
Protein: Amino acids from protein are the building blocks for immune cells and antibodies. Sources like chicken, eggs, and yogurt are good options.
Vitamins and Minerals: Vitamins A, C, and D, along with minerals like zinc and selenium, play crucial roles in immune function. Citrus fruits, berries, and leafy greens are packed with these.
Easy-to-Digest Carbs: Carbohydrates provide quick energy for your body to use. Bland options like toast, rice, and bananas (part of the BRAT diet) are easy on a sensitive stomach.

Making Smart Food Choices When Sick

Warm Broths and Soups: A classic for a reason. Chicken noodle soup provides fluid, electrolytes, and protein, and the warmth can help clear congestion.
Smoothies: A great way to pack in calories, vitamins, and minerals when your appetite is low. Use yogurt, fruit, and even a scoop of protein powder.
Yogurt and Probiotics: Probiotic-rich yogurt can help support gut health, which is vital for a healthy immune system.
Ginger: Known for its anti-nausea properties, ginger tea or ginger ale can soothe an upset stomach.

Comparison of Calorie Intake Strategies When Sick


Strategy	Pros	Cons	Best For
Slightly Increasing Calories (Fever)	Supports higher metabolic rate; fuels immune system; prevents muscle breakdown.	May be difficult if appetite is suppressed; risk of nausea if heavy food is consumed.	Fevers and conditions where metabolic demands increase.
Maintaining Normal Intake (Mild Cold)	Provides consistent energy; easy to manage; prevents nutritional deficits.	May be insufficient if metabolism rises; doesn't account for suppressed appetite.	Mild illnesses with little change in appetite or energy.
Calorie Restriction (Fasting)	None—harmful strategy. Depletes energy reserves; hinders immune function.	Slows recovery; causes muscle breakdown; risks dehydration and nutrient deficiency.	No health benefit, outdated medical myth.
Focus on Nutrient-Dense Calories	Provides essential vitamins and minerals; supports immune function; gentle on the stomach.	May not provide a high volume of calories if appetite is very low.	All illnesses, especially with a reduced appetite.

Conclusion: Fuel Your Recovery, Don't Starve It

Instead of adhering to the outdated notion of 'starving' a fever, the key is to be strategic about your calorie intake. When you are sick, your body requires more energy, not less. While a suppressed appetite might make eating a challenge, focusing on nutrient-dense, easily digestible foods and staying well-hydrated is the most effective approach. By providing your immune system with the necessary fuel, you can support your body’s natural healing processes and work toward a faster, more complete recovery. Listen to your body and give it the nourishment it needs to get back on its feet.

For more information on nutritional support during illness, you can consult with a healthcare professional or review trusted medical resources like MedlinePlus.

Key Takeaways

Increased Metabolic Rate: Your body burns more calories when you're sick, particularly with a fever, to power your immune response.
Fuel, Don't Fast: Fasting during illness is counterproductive, as it starves your immune system of the energy it needs to fight infection effectively.
Listen to Your Body: While you may not want to eat large meals, small, frequent, and nutrient-dense snacks are better than nothing.
Prioritize Nutrients: Focus on calorie-dense foods that also provide essential vitamins, minerals, and proteins, such as chicken soup, smoothies, and fruits.
Hydrate for Healing: Staying hydrated is arguably more important than calories, as fluids are crucial for many bodily functions and can be lost quickly during illness.
Avoid Empty Calories: High-sugar, greasy foods offer little nutritional value and can worsen inflammation, so stick to healthier options.

Frequently Asked Questions

No, you should not force yourself to eat large meals. Instead, focus on consuming small, nutrient-dense snacks and liquids like broth or smoothies throughout the day to provide your body with the energy it needs without causing discomfort.

There is no scientific evidence that links eating, particularly dairy products, to increased mucus production. This is a common misconception. A balanced diet is important for recovery.

This is a myth; both colds and fevers require nutritional support. A fever, in particular, raises your metabolism, increasing your body's need for calories. Restricting calories during a fever can hinder your recovery.

Focus on nutrient-dense foods that are easy to digest. Good options include warm soups and broths, fruits rich in vitamin C like berries, yogurt with probiotics, and bland carbs like toast or rice.

When you have a fever, your metabolism increases. For every degree Celsius your body temperature rises, your energy expenditure increases by approximately 10–13%, requiring more calories to fuel your immune system.

Yes, fasting or severe calorie restriction can be harmful. It depletes your body's energy reserves and can force it to break down muscle protein for fuel, which can slow down the healing process.

Staying hydrated is critical. Drink plenty of fluids like water, herbal teas, and electrolyte-rich beverages like sports drinks or broths to replace fluids lost through sweating.