Running and Ketogenic Diet

Running is one of the most popular aerobic activities, practiced for general well-being, weight loss and athletic performance. In recent years, more and more runners are experimenting with the ketogenic (keto) diet as a nutritional approach to improve body composition and optimize fat metabolism. But is running really compatible with a low-carb, high-fat diet?

Let's analyze the running + keto combination with a technical but accessible look.

📈 What is the ketogenic diet?

The ketogenic diet is based on a drastic reduction in carbohydrates (< 50 g per day), a moderate intake of proteins and a high amount of fats . This setting induces a physiological state called nutritional ketosis , in which the body uses fats and ketone bodies as the primary energy source.

⚡️ Running and Energy Metabolism: An Overview

During running, the body uses mainly muscle glycogen and fatty acids as fuel. At low intensity , fat oxidation prevails; at medium-high intensity , glycogen becomes crucial. Keto fits into this context by modifying the balance between the two substrates.

⚖️ Metabolic adaptation: the transition phase

When switching from a high-carb diet to a keto diet, the body enters an adaptation phase that lasts 2–6 weeks . During this phase:

• Glycogen is dramatically reduced.
• Performance may temporarily decline , especially during high-intensity work.
• The body learns to efficiently oxidize fats and produces ketone bodies.

✅ After adaptation, many athletes report feeling more stable energy , less hunger, and improved aerobic capacity over long distances.

🚀 Low vs High Intensity Performance

• Low intensity (e.g. slow run, aerobic running) :
  • Great context for keto.
  • The body burns mostly fat, even in the absence of carbohydrates.
• High intensity (e.g. repeats, sprints, short races) :
  • Performance may be affected.
  • Glycogen remains the most efficient source for explosiveness.

⚡️ Practical tip : The “ targeted keto ” approach (strategic carbs before or after training) can help during intense sessions by maintaining the state of ketosis.

📅 Recovery and adaptation

One of the limitations of pure keto is the lower availability of glycogen for muscle recovery. Glycogen promotes post-workout protein synthesis and adaptation to training stimuli.

✅ Including a small amount of carbohydrates post-run (e.g. 20–30 g of low GI starches or fruit) can:

• Speed ​​up recovery
• Reduce chronic fatigue
• Don't compromise ketosis, if calibrated

🚰 Hydration and electrolytes

In ketogenic diet there is a physiological reduction in insulin levels, with consequent increase in diuresis and loss of electrolytes (sodium, potassium, magnesium).

🔊 Fundamental:

• Drink more than usual , even 2.5–3 L/day
• Integrate salt (2-3 g per day) and foods rich in potassium and magnesium (e.g. avocado, nuts, bicarbonate-alkaline water)
• Use specific electrolytes during long runs (> 60 minutes)

🛋♀️ Every runner is different: metabolic individuality

Response to keto varies based on:

• Body composition
• Type of training
• Age and gender
• Insulin Sensitivity and Metabolic Status

🔹 Some runners turn into fat-burning machines. 🔹 Others experience performance drops, cramps, or slow recovery.

✅ The important thing is to gradually test and monitor subjective parameters : energy, sleep quality, muscle tone, appetite, HRV (heart rate variability), mood.

🏋️ Conclusion

The ketogenic diet can be a valuable ally for runners , especially over medium-long distances and with the aim of optimizing lipid metabolism, reducing inflammation and improving body composition.

But it is essential:

• Understanding when to use it (type of training)
• Personalize it
• Maintain a good intake of micronutrients, water and electrolytes
• Possibly integrate it with targeted carbohydrates in specific phases

✅ Always consult a sports dietitian or nutrition professional before making drastic changes to your diet.

Recommended approach:

• Long distance running, trail running, slow long runs = great on keto
• Repeats, sprints, speed races = better with a modulated low carb approach

Goal: Run long, well and with stable energy.

🏃♂️🍽️💪