Should I fast on days when I'm sick with a cold, or will it slow my recovery?

Should I fast on days when I'm sick with a cold, or will it slow my recovery?

When you come down with a cold, one of the first things that changes is your appetite. You may not feel like eating at all — or you may feel the pull toward comfort food. If you practice intermittent fasting, you are probably wondering whether to stick to your protocol or abandon it until you feel better.

Short Answer

Fasting when you have a mild cold is generally fine and may even support recovery. The body naturally suppresses appetite during illness because it redirects energy from digestion to immune function. In most cases, this is the body's wisdom at work — not a symptom you need to override. However, if you have a fever, severe symptoms, or a bacterial infection, eating adequately to support recovery becomes more important, and a rigid fasting window should take a back seat.

Detailed Explanation

The Body Already Knows

When you are sick, your brain signals a reduction in appetite through cytokines — the immune messengers released during infection. This is not a malfunction; it is a deliberate shift of metabolic resources. Digesting food is expensive in terms of energy and blood flow. The immune system, running at full capacity to fight infection, benefits when digestion is minimised.

People who force themselves to eat during illness — because they have been told they need to "keep their strength up" — often feel worse immediately afterward. The digestive load competes with immune function rather than supporting it.

What Fasting Does During Illness

During a fast, the body activates autophagy — the cellular recycling process in which the body dismantles and removes damaged proteins, cellular debris, and pathogens. Research has shown that autophagy is upregulated during fasting and plays a role in clearing viral and bacterial debris from cells.

Additionally, fasting reduces systemic inflammation — one of the major drivers of the fatigue, aching, and malaise associated with upper respiratory infections. By lowering insulin and reducing the intake of inflammatory foods, fasting may help the body recover from infection without the added inflammatory burden of digestion.

Upton Sinclair, who documented hundreds of fasting cases in his 1911 book The Fasting Cure, made the same observation over a century ago. He noted that many of his reported cases recovered from acute illness more quickly when they stopped eating entirely and allowed the body to redirect all available energy to healing.

When to Eat Normally Instead

There are situations where pushing through fasting during illness is counterproductive:

• High fever. Fever significantly increases caloric requirements — the body burns more fuel to maintain elevated temperature. Eating normally supports this energy demand.
• Bacterial infections. When your doctor has diagnosed a bacterial infection and prescribed antibiotics, prioritise adequate nutrition to sustain immune function.
• Vomiting or diarrhoea. If you are losing fluids and electrolytes, rehydration and careful nutrition are essential. Fasting during this kind of illness is not appropriate.
• Prolonged illness (more than 3–4 days). If symptoms are severe and extended, eating easily digestible foods helps the body sustain immune function over time.

The Practical Middle Ground

You do not have to rigidly maintain your normal fasting protocol when you are sick. Consider:

• Letting your appetite guide you. If you are genuinely not hungry, do not force yourself to eat. This is the body following its instinct.
• Staying hydrated. Herbal teas, warm water, and electrolytes matter more than food during a cold. Hydration is the highest priority.
• Shortening the eating window rather than eliminating it. Instead of a strict 18-hour fast, a 12–14 hour window may be more appropriate during illness.
• Choosing easy-to-digest foods when you do eat. Warm broth, eggs, cooked vegetables, and easily digested protein are better choices than heavy or high-fat meals during recovery.

Want to learn more? Read our full article: Does Fasting Improve Brain Function and Focus?

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This article is for informational purposes only and is not medical advice. Always consult a qualified healthcare professional before starting any fasting protocol, especially if you have an existing health condition.