It smells like cat urine during exercise – and most people have no idea why. What may at first seem like an unpleasant hygiene issue is, in fact, a metabolic signal. During intense physical activity, the body burns proteins instead of carbohydrates, producing ammonia and releasing the excess through the skin. The sharp, urine-like odour therefore has little to do with cleanliness and much more to do with an imbalance in energy and hydration.
According to sports medicine experts, around seven out of ten recreational athletes experience this phenomenon, especially during fasted workouts or when following a low-carb diet. A 2025 study, “A Micro-to-Macroscale and Multi-Method Investigation of Human Sweating Dynamics,” published on arXiv.org, confirms that ammonia levels in sweat rise significantly during metabolic stress, particularly when carbohydrate stores are depleted. For the editorial team at The WP Times, the topic is both physical and emotional – it shows how the body’s metabolism responds under pressure and how smell subtly influences body image, confidence and social connection.
What Happens Inside the Body
Under normal conditions, the body uses glycogen – stored carbohydrates in the muscles and liver – as its main energy source. When those reserves are depleted through fasting, dieting or prolonged endurance training, the body turns to proteins for fuel. Breaking down amino acids produces ammonia (NH₃), a nitrogen-based by-product that the liver normally converts into urea and the kidneys then filter out.
When training intensity, dehydration or excess protein intake overwhelm these organs, that process becomes incomplete. The surplus ammonia is excreted through sweat glands, causing the characteristic pungent smell reminiscent of cat urine.
Common Triggers in Everyday Training
| Trigger | Description | Result |
|---|---|---|
| Fasted workouts | No carbohydrate intake before exercise | Early protein breakdown, ammonia production |
| Low-carb or high-protein diets | Persistent glycogen deficit | Excess nitrogen and ammonia |
| Protein shakes / BCAA supplements | Surplus amino acids | Liver stress |
| Dehydration | Reduced urea excretion | Ammonia expelled through sweat |
| Overheating / HIIT | Intense metabolism, less oxygen | More waste products via skin |
People who train hard but eat or drink too little are most affected. The body responds with a clear chemical message: I’m running on empty.
Between Metabolism and Mind
An unpleasant body odour affects more than physiology – it influences self-perception. Many exercisers say they feel insecure or embarrassed when they notice this smell. In group classes or yoga sessions, that can lead to social withdrawal – avoiding proximity, holding back effort or skipping sessions altogether. Psychologists describe this as a form of somatic self-awareness: when the body sends a negative signal, the brain interprets it as a threat to belonging or acceptance. Smell thus becomes an emotional stress factor – even when it’s medically harmless.
What Actually Helps – and What Doesn’t
- Eat carbohydrates before training.
A small serving of complex carbs – oats, a banana, or whole-grain bread – stabilises glycogen and prevents protein burn-off. - Stay hydrated.
Drink 500–700 ml of water an hour before exercise, then 100–150 ml every 15 minutes.
After training, replace lost electrolytes with mineral water or coconut water. - Monitor protein intake.
Around 1.2–1.8 g of protein per kilo of body weight is plenty; more adds metabolic stress. - Rest and recover.
Sleep allows the liver to process ammonia efficiently. - Wear breathable fabrics.
Allow sweat to evaporate; tight synthetic clothing traps odour.
Deodorants only mask the smell; they don’t fix the biochemical cause. If the ammonia odour persists, liver and kidney function should be checked medically.
When to See a Doctor
An occasional ammonia smell is harmless. But if it appears regularly or outside of exercise, it’s time for a blood and urine test to check:
- Urea and creatinine – kidney performance
- ALT, AST, GGT – liver enzymes
- Vitamin B12 and folate – protein metabolism
- Blood sugar and ketones – rule out ketoacidosis
Early testing can prevent metabolic strain from developing into an actual disorder.
Smell as a Mirror of Balance
Sweat isn’t just for cooling; it’s the body’s communication channel between organs, chemistry and emotion. A sharp, ammonia-like smell can be an early warning that balance has been lost – in nutrition, hydration, recovery or mental pressure. Recognising such signals isn’t weakness; it’s mindful self-care.
Physical signs are not flaws but invitations to adjust lifestyle before stress or exhaustion take hold.
Sweat that smells like cat urine isn’t a taboo topic – it’s a metabolic message. It shows that training, nutrition and recovery are out of sync. Those who drink enough, refuel with carbohydrates and dose protein sensibly bring their system back into harmony – and regain psychological ease as well.
Health begins where understanding replaces shame. The smell may be unpleasant, but it tells a truth every athlete should know: performance needs balance – and awareness.
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