energy in endurance
Holy Fat Science
The fundamental principles of energy in endurance
In an age of copy-and-paste nutritional advice and marketing trends, confusion often spreads faster than science. At Holyfat, we're going back to metabolic fundamentals. Not slogans.
Here's what physiology actually says about energy, performance, and long-term metabolic health.
Pour optimiser votre stratégie de nutrition sportive, il est essentiel de choisir des apports adaptés à l’effort. Découvrez notamment nos solutions de Purée énergétique, conçues pour soutenir l’endurance, éviter les troubles digestifs et maintenir un niveau d’énergie stable tout au long de la performance.
Myth #1: "You need carbohydrates to perform"
Reality: carbohydrates are a fuel, not energy itself.
The energy usable by the body is called ATP.
It can be produced from carbohydrates, lipids or proteins , depending on the intensity of the effort, its duration and the metabolic state of the athlete.
Carbohydrates allow for rapid ATP production when oxygen demand is very high.
But during the majority of endurance efforts — long, continuous, at low or moderate intensity — lipids are the dominant fuel .
Myth #2: "Lipids are not effective for performance"
Fact: lipids are the densest energy source in the human body.
Weight for weight, lipids provide more than twice the energy of carbohydrates or proteins:
9 kcal/g versus 4 kcal/g.
Even a very lean athlete carries over 30,000 kcal in the form of body fat.
A trained metabolism can access this massive reserve and produce stable, sustainable, and predictable energy, without depending on constant sugar intake.
Myth #3: "You always burn carbohydrates during exercise"
Fact: at low intensity, the body primarily burns fat.
Below approximately 65% of VO₂max (Zone 1 – Zone 2), metabolism primarily uses fats, especially when insulin is low and glycogen stores are not saturated.
The tipping point towards a predominant use of carbohydrates depends on:
– food
– training
– the level of adaptation to lipids
In well-trained endurance athletes, lipids remain the basis of aerobic effort .
Myth #4: "Fat oxidation is genetic"
The reality is: it's a skill that can be trained.
Like strength or endurance, the ability to burn fat develops.
Training in Zone 2, some fasted sessions, a low-sugar diet, and sufficient aerobic volume improve:
– mitochondrial efficiency
– metabolic flexibility
Adapted athletes can oxidize up to 1.5 to 1.85 g of lipids per minute .
It's not a gift. It's an adaptation.
Myth #5: "Lipids are too slow to sustain effort"
Reality: this idea is based on outdated data.
The first studies on fat oxidation were conducted on sedentary subjects.
Among trained athletes, the picture is very different.
At moderate to high intensity, a suitable athlete can produce rapid, stable, and sustained energy from lipids.
Fats are only “slow” if training and diet render them unusable.
Myth #6: "Metabolic health only matters on race day"
The reality is that it is built day by day.
Performance is not solely determined by what happens on the starting line.
It is built in the way the body manages insulin, energy, and recovery each day.
A diet consistently high in sugar during training:
– inhibits fat oxidation
– disrupts hormonal signals
– creates a dependence on rapid intake
You don't repair an engine on race day.
We build it through training.
Myth #7: "You need to apply gel every 40 minutes, even in Zone 2"
Fact: if you train in Zone 2, your body actually learns to burn fat.
Zone 2 is the aerobic engine construction zone.
This is where mitochondria develop.
Bring sugar during these sessions:
– increases insulin
– blocks lipolysis
– diverts metabolism towards carbohydrates
If 80% of your training is aerobic , your diet should support that metabolism — not sabotage it.
Pourquoi la science du “high carb” est appliquée aux mauvais athlètes Ces dernières années, la nutrition sportive est entrée dans une véritable course à l’armement. Les recommandations en glucides pour...