Keto diet

Keto diet is a diet that minimizes carbohydrate intake, using fat as the primary source of energy.

Related reading: The complete guide to proper nutrition — a fundamental guide from the expert team at Sport Zona.

What it is

The ketogenic, or keto diet, is a dietary regimen that radically alters the body's metabolism by significantly restricting carbohydrates in favor of fats. Typically, carbohydrates are limited to 20-50 grams per day, protein is moderate (around 1.2-1.7 grams per kilogram of body weight), and the rest of the calories come from fats. This macronutrient composition forces the body to switch from using glucose as its primary energy source to fats and ketone bodies.

This approach is not new; it has a long history in medical contexts, particularly in treating refractory epilepsy. In recent years, however, the keto diet has gained popularity among the general public, including athletes, due to its potential benefits for weight management, improving metabolic health, and optimizing energy levels.

How it works

When carbohydrate intake is drastically limited, glycogen stores in the liver and muscles are depleted. The body, seeking an alternative fuel source, begins to break down fats into fatty acids. Some of these fatty acids are transported to the liver, where they are converted into ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone). This metabolic process is called ketogenesis, and the state in which the body actively produces and uses ketone bodies for energy is called ketosis.

Ketone bodies can cross the blood-brain barrier and serve as an efficient energy source for the brain, which normally relies on glucose. Additionally, most body cells can also utilize ketone bodies. This shift towards "fat burning" as the primary energy source is the basis of the keto diet's effects. Low insulin levels, induced by low carbohydrate intake, also play a key role by facilitating fat breakdown and inhibiting fat storage.

Key stages of the change:

• Depletion of glycogen stores.
• Increased breakdown of fats.
• Production of ketone bodies in the liver.
• Utilization of ketone bodies for fuel by the brain and muscles.

Why it's important for athletes

For athletes, the keto diet offers several potential benefits, albeit with certain considerations. Primarily, ketosis provides a stable and almost unlimited energy source in the form of fat, which can be beneficial for endurance sports where glycogen stores are quickly depleted. Studies show that trained athletes on a keto diet can adapt their metabolism to burn fat at a significantly higher rate during exercise. Scientific data indicates that the capacity for fat oxidation can reach levels exceeding 1.5 grams per minute during prolonged efforts.

However, the National Strength and Conditioning Association (NSCA) recommends a carbohydrate intake of at least 3-5 g/kg of body weight for athletes engaged in moderate to high levels of activity. On a keto diet, this intake is drastically lower, which can compromise high-intensity activities relying on anaerobic metabolism, such as sprinting or weightlifting. For strength sports, adequate protein intake (1.6-2.2 g/kg of body weight) is critical for maintaining muscle mass, which is possible on a keto diet but may require careful planning to avoid exceeding the moderate level and exiting ketosis. The keto diet can support weight management and body composition by reducing appetite and improving blood sugar control, which is relevant for weight-class sports.

Related concepts

• Ketosis — A metabolic state that is the goal and primary mechanism of the keto diet, where the body uses ketone bodies for energy.
• Carnivore diet — An extreme form of the ketogenic diet that focuses exclusively on animal products, eliminating plant-based foods.
• Gluconeogenesis — The process of synthesizing glucose from non-carbohydrate sources in the liver, important for maintaining blood sugar levels on a keto diet.
• Anabolism — The process of building complex molecules from simpler ones, which can be challenging to maintain in some forms of the keto diet due to limited insulin and carbohydrate availability.