Research
Macro partitioning
Increasing exercise intensity above approximately 75% VO2max downregulates fat oxidation due to decreased adipose blood flow, reduced FFA delivery, and intramuscular inhibition of fatty acid transport and oxidation.
If your goal is to maximize the amount of fat you burn *during* your workout, keep your intensity moderate (around 60-65% of your max oxygen uptake). If you exercise at very high intensities (above 75% VO2max), your body switches to burning mostly carbohydrates because it can't deliver and process fat fast enough to meet the energy demand.
GoodSupportsHIGH confidence
Fat oxidation increases from rest to low- and moderate-intensity exercise (maximum at ~60–65 % VO2max), but decreases at power outputs above approximately 75 % VO2max [29–31]. ... The release of FFAs is decreased from adipose tissue at higher intensities of exercise, most likely due to reduced adipose tissue blood flow, resulting in decreased delivery of FFAs to the contracting muscle.
Why this rating
Supported by multiple studies (refs 29-31, 32, 33) showing consistent trends in human skeletal muscle.
Source
New Insights into the Interaction of Carbohydrate and Fat Metabolism During Exercise
Lawrence L. Spriet · Sports Medicine · 2014
narrative_reviewCited 269×
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