The decision to eat before an early morning workout depends on your specific goals, the type of exercise you plan to do, and how your body responds to food. This choice often involves a trade-off between maximizing performance and avoiding the discomfort of a full stomach. Understanding the science behind fueling and fasting helps you make a personalized decision for your fitness routine.
The Case for Fueling Up
Eating before morning exercise provides readily available energy, which is important for maintaining performance during longer or more intense sessions. Carbohydrates are the body’s preferred fuel source during moderate to high-intensity activity because they are efficiently converted into glucose. This glucose is stored in the liver and muscles as glycogen, which powers your workout.
If you exercise for longer than 60 minutes or engage in high-intensity training, muscle glycogen stores can become depleted. Consuming carbohydrates beforehand “tops off” these stores, preventing early fatigue. A pre-workout meal also helps regulate blood sugar levels, preventing the sluggishness or lightheadedness that occurs when liver glycogen stores run low.
Including a small amount of protein with pre-workout carbohydrates can also be beneficial. Protein consumption prior to exercise supports muscle protein synthesis, the process of building and repairing muscle tissue. This strategy helps mitigate muscle breakdown, particularly during prolonged endurance events or heavy resistance training.
The Case for Exercising Fasted
The argument for exercising in a fasted state focuses on maximizing the body’s reliance on fat as a fuel source. After an overnight fast, reduced liver glycogen levels encourage the body to increase the availability of free fatty acids in the bloodstream. Training in this state promotes metabolic flexibility, improving the body’s ability to switch between using carbohydrates and fat for energy.
This approach is popular among those whose goal is to enhance fat oxidation, or “fat burning,” during the workout. Hormones like norepinephrine and epinephrine are mobilized, assisting in the breakdown of stored fat tissue to fuel the activity. While fasted exercise increases the proportion of fat burned during the workout, studies suggest it does not lead to greater overall fat loss compared to eating before exercise.
Exercising fasted is best suited for low-intensity, steady-state (LISS) cardio or sessions lasting less than 60 minutes. When intensity increases, the body demands glucose quickly, and performance can be impaired without readily available fuel. A fasted workout also simplifies the morning routine and eliminates the risk of gastrointestinal (GI) distress for people who eat too close to exercise.
Practical Pre-Workout Fueling
If you choose to fuel up, the timing and composition of your meal are the most important factors for maximizing benefit and minimizing stomach discomfort. A complete, balanced meal containing complex carbohydrates and lean protein should be consumed two to three hours before your workout. This extended window allows for full digestion and provides sustained energy from complex carbohydrates.
For those with less time, a smaller, easily digestible snack is recommended 30 to 60 minutes before exercise. This snack should focus on simple carbohydrates to provide a quick boost of glucose without weighing down the digestive system. Examples include:
- A medium banana
- A piece of toast
- A handful of dried fruit
- A small portion of low-fat Greek yogurt
Regardless of the timing, minimize the intake of fat and fiber in your immediate pre-workout meal. Both macronutrients slow down the digestive process, which can divert blood flow away from working muscles toward the gut. This can lead to feelings of sluggishness, bloating, or stomach cramps during your session.
Matching Fuel to Workout Type
The decision to eat or not to eat should align with the intensity and duration of the exercise you plan to perform. For short, low-intensity steady-state (LISS) workouts lasting under an hour, training in a fasted state is acceptable and may promote better fat utilization. These activities place a lower overall demand on muscle glycogen stores.
Conversely, any high-intensity activity, such as heavy weightlifting or High-Intensity Interval Training (HIIT), relies heavily on carbohydrate reserves for immediate energy. For these demanding workouts, performance will benefit from pre-exercise fueling to maintain the necessary power and intensity. Similarly, any workout lasting longer than 60 minutes, regardless of intensity, requires pre-workout carbohydrates to prevent mid-session energy depletion.