Research
Mixed
Short-term exposure (1-3 days) to a high-fat, low-CHO diet impairs endurance performance by depleting glycogen without sufficiently increasing fat oxidation capacity to compensate.
Avoid high-fat, low-carb diets for 1-3 days before an endurance event. This will lower your glycogen stores and reduce your ability to oxidize carbohydrates, leading to worse performance without providing enough fat-burning benefits to compensate.
GoodRefutesHIGH confidence
There is clear evidence that short-term 'fat loading' is detrimental to endurance capacity and the performance of prolonged exercise.
Why this rating
Supported by multiple studies cited in the text showing performance impairment.
Source
Effects of short-term fat adaptation on metabolism and performance of prolonged exercise
Louise M. Burke et al. · Medicine & Science in Sports & Exercise · 2002
DOI 10.1097/00005768-200209000-00015
narrative_reviewCited 111×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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