Why Does Your Body Crave Junk Food When You're Sick?

November 16, 2025 •

4 min read

According to biomedical science experts, when your immune system activates to fight an illness, its energy demands increase significantly. This triggers a complex chain of physiological and psychological responses that can explain why your body craves junk food when you're sick. It is a paradox where a suppressed appetite can be accompanied by an intense desire for certain high-calorie items.

Quick Summary

The biological and psychological reasons for junk food cravings during illness are explored. The body's immune response requires extra energy, hormonal shifts occur, and the brain's reward system seeks comfort. These factors combine to make high-calorie foods appealing, even if they aren't the best choice for recovery.

Key Points

Immune System Requires Energy: Your immune system works overtime when you're sick, dramatically increasing your body's energy demands.
Hormonal Stress Response: Illness activates the stress response, causing a release of cortisol that drives cravings for high-calorie, comforting foods.
Brain's Reward System: Eating sugary and fatty foods releases dopamine, creating a temporary feeling of pleasure that the brain seeks to alleviate discomfort.
Gut Microbiome Influence: The balance of bacteria in your gut can be altered during illness, with some microbes potentially increasing cravings for sugar.
Short-Term vs. Long-Term Effects: While junk food provides a quick energy fix, it can increase inflammation and lead to energy crashes, hindering long-term recovery.
Healthier Alternatives: Substituting junk food with nutrient-dense options like fruits, soups, and whole grains can effectively satisfy cravings while supporting your immune system.

When you are feeling unwell, it might seem counterintuitive that your body suddenly wants salty, sugary, and fatty foods. While many people experience a complete loss of appetite, others are overwhelmed by the desire for specific, often unhealthy, foods. The truth is, there is a complex biological and psychological explanation behind this phenomenon. Your body is engaging in a primitive, instinct-driven behavior aimed at short-term survival, though the modern results may be counterproductive.

The Immune System's High Energy Demands

The primary driver behind your junk food cravings is the immune system's activation. When a virus or bacteria invades, your body shifts into high gear to fight the infection. This requires a significant amount of energy, and your metabolism increases to support the heightened activity. As one study suggests, a fever can increase your basal metabolic rate by as much as 7% for every 0.5°C rise in body temperature. Your body perceives this energy deficit and seeks out the quickest, most efficient source of fuel available: simple carbohydrates and fats found in junk food. This is a primal survival mechanism designed to ensure a quick energy boost is readily available during a crisis.

Hormonal and Neurological Changes

Beyond simple energy demands, a cascade of hormonal and neurological changes occur during illness that specifically encourage junk food cravings.

Cortisol Release: Stress, whether physical from illness or psychological, triggers the release of cortisol. This hormone helps to mobilize stored energy but also increases your preference for high-calorie, sugary, and fatty comfort foods. This creates a vicious cycle where feeling unwell and stressed increases the desire for junk food, which in turn spikes blood sugar and can lead to a crash.
The Dopamine Reward System: Eating sugary and high-fat foods triggers the brain's reward system, releasing neurotransmitters like dopamine and serotonin. These are often called 'feel-good' chemicals because they produce a temporary sense of pleasure and comfort. When you are feeling miserable, your brain actively seeks out this reward pathway to alleviate the emotional discomfort of being sick.
Ghrelin, the Hunger Hormone: The body's heightened metabolic state and recovery process can increase the secretion of ghrelin, the 'hunger hormone'. This hormone signals to the brain that it's time to eat, specifically promoting the desire for high-calorie, carb-laden foods to meet the increased energy needs.
Gut Microbiome Shifts: There is growing evidence that the trillions of microorganisms in our gut, known as the microbiome, can influence our cravings. Some studies in mice have suggested that specific microbes can drive sugar cravings, especially after antibiotic use, which disrupts the gut flora. While still being researched, this indicates that the bacterial makeup of your gut may also play a role in your desire for certain foods during illness.

The Negative Feedback Loop of Junk Food

While junk food may offer a temporary feel-good boost, it is generally detrimental to the long-term recovery process. The initial sugar rush is often followed by a crash, leading to heightened fatigue and decreased alertness. Furthermore, a diet high in processed sugars and fats promotes systemic inflammation, which can exacerbate the symptoms of illness. The nutrient-poor nature of junk food also means you miss out on the vital vitamins, minerals, and antioxidants your body desperately needs to fight off infection and heal.

Comparison: Junk Food vs. Nutrient-Dense Food When Sick


Feature	Junk Food	Nutrient-Dense Food
Energy Release	Rapid spikes and crashes, leading to short-term boost followed by fatigue.	Sustained energy supply, preventing energy slumps.
Nutrient Content	Generally nutrient-poor, lacking essential vitamins and minerals.	Rich in vitamins, minerals, and antioxidants essential for immune function.
Inflammatory Effect	Can promote and worsen inflammation in the body.	Often contains anti-inflammatory compounds that aid in recovery.
Digestive Impact	Can be difficult for an already compromised digestive system to process, potentially causing further discomfort.	Typically easier to digest (e.g., soups, broths).
Mood Impact	Provides a temporary feel-good dopamine hit but can be followed by guilt and a worsened mood.	Nourishes the body and brain, contributing to overall well-being and a healthier mood.
Immune Support	Can impair white blood cell function and hinder recovery.	Actively supports immune cells and antibody production.

Healthier Alternatives to Satisfy Cravings

Satisfying your body's innate drive for energy and comfort during illness doesn't have to mean resorting to unhealthy food. You can make smarter choices that aid your recovery while still providing a sense of comfort.

For Sweet Cravings: Reach for fresh fruits like bananas or berries, or add honey to herbal tea. Natural sugars provide energy along with vitamins and antioxidants without the inflammatory side effects of refined sugar.
For Salty Cravings: Opt for a bowl of warm, nutrient-rich broth or homemade chicken soup. These provide hydration and electrolytes, and the warmth can be very soothing. You could also try low-sodium crackers or roasted vegetables with a pinch of salt.
For Carb Cravings: Choose complex carbohydrates that offer sustained energy, such as whole-grain toast, oatmeal, or brown rice.
For Creamy/Fatty Cravings: Consider natural yogurt with a little fruit or a serving of avocado toast. These offer healthy fats that provide satiety and energy.
Consider Probiotics: Since gut health can be a factor, incorporating probiotic-rich foods like yogurt or kefir can help restore a healthy balance of gut bacteria.

Conclusion

Understanding why your body craves junk food when you're sick reveals a fascinating interplay of biological and psychological mechanisms. Your immune system's need for a quick energy source, coupled with hormonal shifts and the brain's search for comfort, drives these desires. While indulging occasionally is understandable, opting for nutrient-rich alternatives will better support your body's recovery. By listening to what your body truly needs—sustained energy and healing nutrients—you can address your cravings in a way that promotes a quicker, more robust recovery rather than a temporary and ultimately counterproductive comfort.

For more information on the mind-body connection during illness, the National Institutes of Health provides numerous studies and resources on the effects of diet on immune function and inflammation.

Frequently Asked Questions

While a small amount of junk food may feel comforting, it's not ideal for recovery. Refined sugars and fats can increase inflammation and lead to energy crashes, potentially slowing down your healing process.

For sweet cravings, try fruits like bananas or honey in tea. For salty desires, reach for nourishing broths or soups. Complex carbohydrates like oatmeal and probiotic yogurt are also good choices for sustained energy and gut health.

Yes, especially if you have a fever. The immune system's intense activity increases your metabolic rate, which requires more energy and burns extra calories.

Comfort foods are often associated with positive childhood memories and feelings of safety. When you're unwell, your brain seeks out these familiar, high-calorie foods to trigger feel-good neurotransmitters like serotonin and dopamine.

Yes, the stress of illness releases hormones like cortisol. This can sometimes suppress your appetite, but it can also increase your preference for high-calorie, high-fat foods, creating competing signals in your body.

While illness can deplete important nutrients, the primary drivers for junk food cravings when sick are the immune system's energy needs and hormonal changes. However, some nutritional deficiencies, like low magnesium, can be linked to sugar cravings in general.

An imbalance in your gut microbiome, often caused by illness or medication like antibiotics, can influence cravings. Some studies suggest certain gut microbes can increase the desire for sugary foods.