Yohimbine is an extract found in some pre-workout and fat-burning supplements. While it may be an effective stimulant, it can also cause an upset stomach and other adverse effects3.
In my experience, taking yohimbine on an empty stomach can result in “emergency evacuation.” For this reason, I wouldn’t recommend using a pre-workout containing this compound if you workout fasted.
6. Added Sugars
In addition, some pre-workouts contain artificial sweeteners known as sugar alcohols for flavoring. However, these zero-calorie additives don’t absorb well in the gut and can cause diarrhea in some people.
Lastly, unless you’re “dry scooping,” you probably mix your pre-workout powder with water. And drinking a glass of water is a surefire way to get your digestive system moving, especially in the morning.
One way around this is to take your pre-workout with less water. As little as 3 ounces is usually enough to dissolve the powder. Just make sure you drink plenty of water throughout the day!