Why We Can’t Talk About the Ketogenic Diet and Optimal Performance

Why We Can’t Talk About the Ketogenic Diet and Optimal Performance
by Laurent Glatz – for Athletic Carnivore

Functioning is not optimizing. This is probably the most common misunderstanding when discussing ketosis, sports, and performance. The human body can function very well with very few carbohydrates. It can even regain remarkable stability when modern diets have trapped it in the rollercoaster of blood sugar, insulin, hunger, and fatigue. But optimal performance is not defined by the ability to stand, train adequately, or finish a race. It is defined by the ability to express the highest possible level of power, speed, repetition, explosiveness, recovery, and adaptation.

The problem is therefore not whether the ketogenic diet works. It does. It can stabilize energy, improve satiety, reduce hyperinsulinemia, facilitate fat oxidation, and make an athlete more autonomous during long efforts. But as soon as we talk about the optimum, the vocabulary must change. The optimum requires not only a large fuel reservoir but also a sufficient energy flow at the exact moment the muscle demands it.

Fat is an immense fuel source, but it is slow. It goes through a highly efficient mitochondrial machinery to produce a lot of ATP, but this production is not as rapid as glycolysis when intensity explodes. A sprint, a heavy set, a surge, a steep hill, a late-race acceleration, or repeated threshold efforts don’t just demand energy—they demand energy fast. This is where glycogen takes center stage again.

Simplistic discourse often claims that since fat stores are enormous and glycogen stores limited, fat must be the superior fuel. This logic overlooks a crucial concept: a fuel is only superior in the context where it meets the demand. For walking long distances, cycling at low pace, maintaining steady endurance, or getting through a day without cravings, lipid oxidation is a biological marvel. To produce high power output, it becomes insufficient on its own.

In ketosis, glycogen is not absent. The liver continues to produce glucose via gluconeogenesis. Muscles retain some reserves. But presence does not mean maximum availability, and availability does not mean optimal flow. A ketogenic athlete can certainly produce powerful efforts, but they impose a constraint on their system. They ask the body to preserve a pathway that, in certain disciplines, becomes decisive.

In strength training, this limitation is often misunderstood. A single maximal effort does not heavily depend on carbohydrates. But real training is not a single movement. It’s volume, sets, repetitions, rest periods, an accumulation of mechanical tension, the ability to maintain contraction speed, and to repeat multiple times per week. The higher the volume, the more glycolysis matters. The practitioner can still train, but the question becomes: can they reach their full potential?

In endurance, the confusion is even greater. Ketosis can be an advantage for long, low-intensity efforts. It reduces reliance on fueling, smooths energy, and limits some energy crashes. But competitive endurance is not a biological treadmill. There are pace changes, climbs, attacks, descents, race finishes—moments when you must step out of lipid comfort. Even in ultra-endurance, many athletes strategically reintroduce carbohydrates when the event surpasses a certain level of demand.

The hormonal context adds a decisive layer. Lower insulin increases sodium excretion by the kidneys. If sodium is not adjusted, circulating volume drops, functional pressure decreases, contractions feel flat, and recovery worsens. Cortisol can also rise when the body must maintain blood sugar under heavy training loads, especially if sleep, calories, or electrolytes are insufficient. The body doesn’t cheat: it compensates.

Leptin and ghrelin also remind us that ketosis does not abolish the laws of energy availability. A very lean, highly active athlete in deficit or chronic stress may experience disrupted hunger, fragile sleep, and reduced recovery. Ketogenic satiety is useful as long as it doesn’t mask a real lack of intake. For some athletes, eating less initially feels comfortable but then becomes an invisible barrier to progress.

This is where the carnivore logic deserves distinction from theoretical ketogenic diets. A well-constructed carnivore diet can provide complete proteins, heme iron, zinc, creatine, carnosine, cholesterol, animal fats, and a nutritional density hard to match. It can rebuild a damaged foundation. But if it remains strictly ketogenic in a discipline where glycolytic flow makes the difference, it must be considered a tool, not a religion.

The real debate is therefore not “ketogenic or not ketogenic.” The real debate is: what effort demands what fuel, at what moment, in which body, under what stress level, and with what real goal? Saying ketosis can help many people is true. Saying it automatically represents optimal performance is biologically too simplistic.

The remaining question is simple: are you looking for a diet that lets you function properly, or a strategy that allows you to express the full ceiling of your physiology?

#Ketogenic #SportsPerformance #Glycogen #Metabolism #Carnivore #Insulin #Cortisol #Endurance #StrengthTraining #AthleticCarnivore