Not All “Healthy” Foods Are Workout Friendly: A Registered Dietitian’s Guide on Pre-Workout Snacking

Most people think about what they should eat before a workout. A quick carb for energy. A bit of protein for muscle repair. Enough fluids to support performance. These choices matter. Yet many foods that support long-term health can cause discomfort when eaten too close to exercise.

Timing affects digestion, energy availability and how your stomach responds to movement. Even nutritious foods can work against you if they sit too heavy or digest too slowly. As a dietitian, I often see clients struggle not because their choices are unhealthy but because the timing does not suit their workout.

4 Healthy Foods Not Appropriate as Pre-Workout Snacks

The four foods below are excellent for your diet in general but may not be ideal in the one to two hours before exercise.

1. High fat foods slow your warm-up

Healthy fats offer many benefits. They support hormone production, help you absorb vitamins and keep you full. Nuts, nut butter, avocado, chia pudding and trail mix all fit well into a balanced diet. The challenge is that fat takes longer to digest.

During exercise, blood flow shifts toward your muscles. Less blood moves to the digestive tract. Digestion slows. This can lead to early feelings of heaviness or mild nausea.

Research supports this effect. A controlled trial¹ found that gastric emptying was “much slower with [fat] compared with water,” highlighting how fat-rich meals remain in the stomach longer.

These foods are still healthy. They simply work better when eaten two to three hours before training.

2. Large protein shakes can feel too heavy

Protein supports muscle repair. Many people drink protein shakes right before they exercise. This works for some, but for others, a large, nutrient-dense shake can feel heavy.

Protein takes longer to digest than carbohydrates. A big shake with dairy, nut butter or seeds stays in the stomach for a longer time. Your body then redirects blood flow to your muscles, leaving digestion to work with less support.

A randomized trial² in well-trained basketball players found that a pre-exercise meal containing protein and carbohydrate increased nausea during exercise. The authors reported that “nausea during and post-exercise increased following PRO/CHO [protein + carbohydrate]” and noted that the added protein “may have increased nausea during exercise”.

Protein is still essential. You can include a small amount before exercise, but large shakes may be better consumed earlier in the day or after your workout.

3. High fibre foods raise the risk of discomfort

Vegetables, beans, lentils and whole grains support long-term gut and heart health. They add bulk, promote regularity and help with satiety. These benefits are important, but they can be problematic during a workout.

Fibre increases stomach volume and promotes fermentation in the large intestine. This can lead to bloating, gas or cramping when eaten close to exercise. Movement adds pressure. Running, jumping or twisting can make these sensations more noticeable.

Sports nutrition research supports adjusting fibre intake around training. One review³ advises avoiding high fibre foods before competition, noting that they “may result in unnecessary gas production which might cause cramping”.

You do not need to avoid fibre. Just schedule high fibre meals earlier in the day if you plan to work out soon.

4. Fermented or probiotic foods can be unpredictable

Fermented foods support a diverse gut microbiome. Kimchi, sauerkraut, kombucha, kefir and miso all contain beneficial bacteria. Many people tolerate these foods well. Others experience more gas or faster bowel movements, depending on gut sensitivity.

Fermented foods often contain organic acids and gas from the fermentation process. These may stimulate the gut. During exercise, especially with bending or twisting motions, this can feel uncomfortable.

A 2023 systematic review⁴ on gastrointestinal symptoms during exercise notes that foods that increase gas production or gut motility raise the risk of discomfort during movement.

These foods remain excellent for health. They simply work better when eaten away from workout times or after you know how your body responds to them.

Better Pre-Workout Choices

If you have less than 2 hours, the best pre-workout foods digest easily and provide quick energy. Carbohydrates fit this purpose well. You can pair them with a small amount of protein if needed.

Try these:

• A banana
• Toast with a thin layer of peanut butter
• A small yogurt
• A simple fruit smoothie
• A rice cake with cottage cheese
• Oatmeal if you have more than an hour

If your workout starts soon, choose simple carbohydrates. If you have two to three hours, enjoy a balanced meal with lean protein, complex carbs and moderate fat.

Pre-workout nutrition does not need to be complicated. The four foods above remain healthy choices. They simply perform better at other times of the day. A few small timing adjustments can help you feel lighter, more comfortable and more energized during your workouts. golden rule of eating familiar foods before a race or competition. This would not be the time to try something new! Trial and error during training will help you find the fuel that will work best for you.

1. Gentilcore, D., et al. “Effects of Fat on Gastric Emptying of and the Glycemic, Insulin, and Incretin Responses to a Carbohydrate Meal in Type 2 Diabetes.” The Journal of Clinical Endocrinology & Metabolism, vol. 91, no. 6, 2006, pp. 2062–2067. https://academic.oup.com/jcem/article/91/6/2062/2843371
2. Gentle, H., et al. “A Randomised Trial of Pre-Exercise Meal Composition on Performance and Muscle Damage in Well-Trained Basketball Players.” Journal of the International Society of Sports Nutrition, vol. 11, 2014, article 33. https://jissn.biomedcentral.com/articles/10.1186/1550-2783-11-33
3. Oliveira, Erick Prado de, and Roberto Carlos Burini. “Nutritional Recommendations to Avoid Gastrointestinal Distress during Exercise.” Sports Science Exchange, vol. 27, no. 114, 2014. https://www.gssiweb.org/sports-science-exchange/article/sse-114-nutritional-recommendations-to-avoid-gastrointestinal-distress-during-exercise
4. Hughes, William G., et al. “Exploring the Gut-Exercise Link: A Systematic Review of Gastrointestinal Symptoms, Nutrition and Exercise.” World Journal of Gastroenterology, vol. 31, no. 22, 2023, pp. 106835, https://www.wjgnet.com/1007-9327/full/v31/i22/106835.htm