One of the unpleasant side effects of vigorous exercise is body odor. When you sweat, bacteria on your skin naturally produce that familiar locker room aroma. But during prolonged exercise, you may notice an acid or ammonia odor that is different from your usual armpit fare.
That chemical smell in your nose after exercise is related to the breakdown of amino acids, and may indicate that you need to tweak your nutrition.
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Energy in the Human Body
When you exercise, your body's first choice of fuel is carbohydrate, found in the form of glucose in the blood and glycogen in the muscles and liver. As glucose stores become depleted during long-duration, low-intensity rhythmic activities, including running or cycling, your body will gradually draw on fat stores for energy.
But because fat is an oxidative fuel, your body cannot use it for prolonged high-intensity activities, and it will begin to break down protein from muscle to satisfy its energy needs.
Read more: Ew! Why Do I Sweat So Much When I Work Out?
What's That Smell?
The onset of protein breakdown is often marked by an ammonia odor in the sweat and on the breath. Ammonia, whose chemical structure is NH3, is a metabolic byproduct of the stripping away of the nitrogen molecule from amino acids so the remaining carbon can be converted to glucose.
The nitrogen then bonds with hydrogen to form ammonia, a component of urea, and eventually leaves the body via the urine, in sweat and in moisture expired on your breath.
Carbohydrate Intake and Performance
When amino acids are broken down during prolonged exercise, ammonia levels in the central nervous system and the brain increase significantly. According to a 2018 study published by Journal of Earth and Environmental Sciences, ammonia production is higher when the intensity of exercise increases.
The article also points out that past research has shown that ammonia levels are higher in individuals who exercise in a state of carbohydrate depletion. Consuming more carbohydrates can help reduce the ammonia smell you experience after a workout.
Stay Hydrated and Snack
Dehydration is another factor in the ammonia smell — be sure to stay hydrated throughout the day and during exercise activities. Dehydration makes your sweat more concentrated, which can increase the odor. Make sure your urine is straw colored, not dark yellow or brown.
Many people skimp on carbohydrates for fear of gaining weight. However, ample carbohydrate consumption from high-quality whole food sources and hydration before your workout can enhance and prolong performance, netting you a greater caloric burn while sparing lean mass. Consuming more protein will not spare muscle and will tax the kidneys. A diet containing an ample balance of complex carbohydrates will give you a leaner, more powerful physique in the long run.
Read more: Lack of Sweating During Exercise
See a Doctor
Although sweat is a normal part of life, particularly when you are exercising, there are underlying medical conditions that can contribute. According to Mayo Clinic, consult your doctor if you notice a sudden change in the smell of your body odor, experience night sweats, start sweating significantly more than usual or if your sweating interferes with your daily tasks.
- Journal of Earth and Environmental Sciences: "Influence of exercise on plasma ammonia and urea after ingestion beverages of carbohydrate electrolyte"
- Progress in Molecular Biology and Translational Science: "Exercise and regulation of carbohydrate metabolism"
- Nutrition Today: "High-Quality Carbohydrates and Physical Performance"
- Mayo Clinic: "Sweating and Body Odor"