The Exercise + Low Carb Playbook: What to Eat Before, During and After a Workout
For decades, exercisers were told they needed sports drinks, energy gels and carb-rich meals to fuel workouts or competitions. But research suggests that recreational exercisers and people participating in endurance exercise or moderate-intensity activities may perform quite well eating fewer carbs, especially once they become more efficient at using fat for fuel. The key is how to fuel your workouts strategically before, during and after exercise to support energy, recovery and muscle growth.
How Your Body Fuels Exercise
Your body primarily relies on two fuel sources during exercise:
- Carbohydrates (stored as glycogen)
- Fat (stored in adipose tissue and muscle tissue)
The proportion of each fuel used depends on several factors, including exercise intensity, duration, fitness level, and diet.
During lower-intensity activities such as walking, hiking, cycling, yoga, or easy jogging, the body relies heavily on fat for fuel. As exercise intensity increases, carbohydrate use generally increases because glycogen can provide energy more rapidly.
Studies have consistently shown that eating around 100 grams of net carbs per day or fewer gradually teaches your body to become more efficient at accessing and utilizing fat stores, a process often called fat adaptation.
What is Fat Adaptation?
When you reduce your carb intake, insulin levels typically decrease, encouraging your body to tap into stored fat for energy. Over time, your metabolism becomes more efficient at burning fat during exercise.
The Benefits of Combining Exercise + Low Carb
One of the biggest advantages of a low carb approach is the potential to increase fat burning. By lowering carbohydrate intake, your body becomes more efficient at using fat for energy even at higher intensities.
Better Blood Sugar Control
Exercise independently improves insulin sensitivity, helping muscles absorb nutrients more effectively. When paired with a lower-carb eating pattern, many people experience greater improvements in blood sugar regulation and metabolic health.
This combination may be especially helpful if you have prediabetes, type-2 diabetes, metabolic syndrome or insulin resistance.
Increased Metabolic Flexibility
Metabolic flexibility refers to your body's ability to switch between burning carbohydrates, fat, and ketones depending on activity levels and energy demands.
Modern diets high in refined carbohydrates can reduce this flexibility over time. Low carb eating, combined with regular exercise, helps retrain your body to efficiently use multiple fuel sources.
Improved Body Composition
Exercise, especially resistance training, may help preserve and build lean muscle mass—helping improve body composition. When combined with adequate protein intake and a carb conscious mentality, scientific reviews conclude you may lose body fat while maintaining more muscle compared to dieting alone.
This is particularly important as we age since muscle loss naturally accelerates beginning in midlife.
Pre-Workout Nutrition: Keep It Small and Stable
Eating too much before exercise (especially a high-protein or high-fiber meal) may lead to digestive discomfort and unstable blood sugar levels. For someone watching their carb intake, your ideal pre-workout stack is small, easy to digest, moderate in fat and low in fiber.
Examples include:
- A small piece of cheese and an apple
- A handful of nuts
- Half an Atkins ready-to-drink shake
- A no or low-sugar electrolyte beverage
What to Eat During Exercise
For most workouts, you don’t need too much food (if any) during exercise, although a no or low-sugar electrolyte drink is also an option.
However, a comprehensive review of over 160 studies suggests that during prolonged exercise, particularly beyond 70 minutes, small amounts of carbohydrates may help manage blood sugar levels and delay fatigue.
Examples include:
- A small serving of fruit (i.e., a banana once you’re past the 70-minute mark of exercise)
- A low-sugar sports beverage
- Strategic carb supplementation for endurance events
The goal isn’t to “refuel” completely during exercise, but rather to prevent big drops in blood sugar that changes how your brain perceives energy availability and thus affects your performance or energy.
Post-Workout Recovery
What you eat after your workout matters the most. And protein plays a critical role in muscle repair, growth and recovery. You may include some carbs with your protein in this post-workout meal, which you should have within 1 to 2 hours of your workout. This is your anabolic sweet spot, when your muscles and body are primed and ready to receive and process protein and some carbs.
Examples include:
- Atkins shakes
- Any smoothie made with high-quality protein powder, such as a Blueberry Almond Protein Smoothie or Vanilla Lemon Ginger Recovery Shake
- Greek yogurt
- Cottage cheese
- Eggs
- Chicken
- Fish
- Lean meat
Most people benefit from about 20 to 40 grams of protein after exercise, depending on body size, age and training volume. For many adults over 40, post-workout protein intake may be even more important, as age-related muscle loss (sarcopenia) accelerates.
Most high-quality protein sources also contain an important amino acid called leucine, which is crucial for muscle growth, recovery, weight control and blood sugar management. The best sources of leucine are typically animal proteins, but they can also be obtained through some plant-based foods.
Some Top Sources of Leucine
- Whey Protein
- Cottage Cheese
- Beef
- Salmon
- Eggs
- Nuts
- Soy
Exercise + Low Carb = A Personalized Approach
Regular exercise and eating fewer carbs may work together to help improve metabolic health, support fat burning, preserve muscle and promote long-term weight management.
The most important nutrition strategies for exercise include:
- Keeping pre-workout meals light
- Prioritizing hydration
- Using carbs strategically when appropriate
- Consuming protein within an hour or two of exercise
- Focusing on muscle preservation and growth, as well as weight loss
Rather than following traditional carb-loading advice, today's exercisers may benefit from a more personalized approach.
Jon Clinthorne, PhD
Sr. Director of Nutrition