Why Do I Feel Nauseous After Working Out? We Asked a Dietitian

workout nausea


Have you ever been struck by a bout of post-workout nausea? You’re not alone. For some, a gym session is often followed by a sudden spell of wooziness, leaving us asking what the heck is going on inside our bodies and wondering if the feeling is normal.

Except for rare extreme cases, the good news is there’s no reason to worry. Exercise-induced nausea is a common issue affecting many of us and for a diversity of reasons.

Understanding why it happens will help you tweak workouts accordingly (and better focus on your burpees and not the unsettling pit in your belly). Let’s break down some of those nausea-inducing culprits.

Meet the Expert

Melissa Nieves is a Registered Dietitian and licensed dietitian nutritionist at Kemtai, the digital, home-fitness company.

Eating Too Soon Before or After

Let's start off with an obvious offender: eating too soon before a workout. Following a meal, the body is in digestion mode, and launching our bodies into an exercise routine is one way to bring on nausea. Just as we're told not to lie down immediately after eating, the same can be said for working out.

“Eating around three hours before working out can help alleviate GI discomfort as blood flowing to our GI tract and stomach is rerouted to the muscles when we work out, therefore slowing the digestion of food in our stomach,” explains Nieves. “Easy-to-digest foods such as dry toast, dry cereal, bananas, crackers, yogurt, fruits and vegetables are some good choices, as well as avoiding high fat and fried foods before working out as they’re more likely to cause discomfort." Not to mention that when your blood sugar drops, signals are fired off—one being nausea.

What you eat post-workout is just as important in reducing the chance of nausea, given the body is adjusting back to its normal rhythm. After exercise, our bodies enter a state of repair—the optimum time for a refuel. Combine a light protein-filled snack to kick in the muscle building effect, alongside carbohydrates to replenish our depleted glycogen stores to reap all the benefits. Banana and nut butter is a delicious go-to.

Intensity of a Workout Session

A sweaty session of jump-tucks, high-knees and lunge-kicks will shake around the insides more than an hour of gentle yoga. It’s this high expel of energy that causes a churning feeling to creep in, especially when launching from zero to 100 right off the bat. “Usually, high intensity workouts, where a lot of sweat is lost, can bring on nausea, mainly due to dehydration,” explains Nieves.

Just as we should ease our bodies into a workout to gradually fire up the muscles and lubricate the joints, ending a workout properly is also key to slowing the body down rather than shifting between extremes.

“Starting or stopping exercise abruptly, as well as spurts of overexertion, are factors attributing to nausea, and so it's best to check in with yourself during your workout and pace it out,” suggests Nieves. “Take the time to start off slowly and cool down accordingly, such as transitioning from a run, to a light jog, to a walk, until you feel more comfortable, with a relaxing stretch to round things off and let the body settle down.”

Also, think about it: dynamic workouts often invoke twisting, jumping, turning, and altering from lying, to seated, to standing positions (and everything in between). That’s a lot of sloshing around and compression to our insides. In any intense or high impact sport, it’s vital to commence gently instead of jumping straight off the diving board. For those new to the gym floor, take a lead from the trainer or instructor and dial down the tempo if exercises become too much.

Fluid Intake

Dehydration, which can set in from just a 5-8% fluid loss and cause a host of symptoms including fatigue and vomiting, is another major contributor to workout-induced nausea.

"Whether an intense or low impact workout, in a hot climate or cold, we need to replenish fluids. The question is, what counts as too little or too much when drinking during a workout, and can either lead to an unwanted side effect?” poses Nieves. According to the American College of Sports Medicine, the rule of thumb is to drink on a 1:1 ratio, meaning you should drink as much water as you lose, and not drop below a 2% loss in fluids overall.

But did you know that drinking too much water has dangers of its own, which can, according to Neives, dilute your electrolyte levels and in turn can lower sodium concentration in the blood? “Hyponatremia is a sign that you drank too much water and have thus diluted your electrolyte levels, which may lead to a low sodium concentration in the blood.” Both dehydration and hyponatremia can spark nausea and other unpleasant symptoms, namely dizziness and muscle weakness, among others.

How to solve it? Keep your water intake in balance with your workout length and intensity.

Underlying Medical Condition

Some medical conditions may induce an onset of nausea during or after workouts, including stomach-related discomforts such as irritable bowel syndrome, affecting between 10-15% of the US adult population, or an attack of vertigo, which is when a person experiences a dizzying or "spinning" sensation around them.

In such cases where medications or supplements are required to treat a medical condition, an uneasy feeling in the stomach can sneak up on us. For example, the drugs used to treat those who are hyperglycaemic or hypoglycemic may cause nausea as a side effect. Similarly, supplements taken to increase iron levels or boost our vitamin C intake may give off symptoms of nausea.

“If ingested immediately before a workout, some medications and supplements may increase acid production in the stomach, leading to a feeling of discomfort, especially those containing high levels of vitamin C and iron which can irritate the stomach lining,” explains Nieves. “Many supplements are better tolerated when taken alongside food, rather than on an empty stomach, which can effectively reduce this unwanted side effect. However, it's best practice to consult with a healthcare professional on how to take medication and supplements depending on your individual condition.”

The Bottom Line

Nausea is a common side effect of exercise which can spring on any of us, regardless of fitness level or workout intensity. From lack—or excess—of fluids, to eating hard-to-digest foods, or skipping the warm up, there’s a diversity of reasons for a queasy feeling to strike. However, there are simple ways to ward it off, including hydrating sufficiently prior to, during, and after exercise, leaving ample time to eat before hitting the mat, and guiding your body into the flow with a dynamic warm-up, rounding off with a relaxing stretch to harmonize the body and mind.

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