Macro partitioning
Long-term adaptation (several months) to a low-carbohydrate-high-fat (LCHF) diet enhances endurance performance in ultra-endurance events by increasing maximal fat oxidation rates and sparing muscle glycogen, without compromising glycogen resynthesis.
If you are an endurance athlete, switching to a low-carb, high-fat diet requires patience. You must stick to it for several months (at least 6) to allow your body to adapt metabolically. Once adapted, you can burn fat much faster (up to 1.5 g/min) and spare your muscle glycogen, which may help you maintain intensity in very long events like marathons or triathlons. Do not expect immediate performance gains; the metabolic shift takes time.
Long-term adaptation to LCHF diets produces even greater metabolic benefits, including a higher rate of fat oxidation and lower rates of carbohydrate oxidation and glycogenolysis. Endurance athletes who adapted to LCHF diets for 9-36 months could reach the maximal fat oxidation rate of approximately 1.5 g/min... These metabolic adaptations to LCHF diets may benefit endurance performance. Thus, it has been hypothesized that long-term LCHF diet may enhance performance in ultra-endurance events such as the ultra-marathon and ironman triathlon by supporting a higher fat oxidation rate at higher relative exercise intensity and by having a glycogen sparing effect.
Why this rating
The paper is a review citing multiple studies (Burke, Volek, Phinney) showing metabolic shifts, but notes that direct performance trials in race-like designs are still needed.
Source
Low-Carbohydrate-High-Fat Diet: Can it Help Exercise Performance?
Chen‐Kang Chang et al. · Journal of Human Kinetics · 2017
DOI 10.1515/hukin-2017-0025
More from this paper
- Long-term LCHF diet adaptation may improve performance in repeated high-intensity exercise (e.g., field sports) by maintaining power output in later stages of competition through increased fat oxidation and glycogen sparing.Moderate
- Long-term LCHF diet adaptation may lead to the early development of central fatigue during exercise due to elevated blood concentrations of non-esterified fatty acids (NEFA) and ammonia.Moderate
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