Fat Max is the exercise intensity at which the highest rate of fat oxidation is observed during a test.
It is estimated using respiratory gas exchange and the respiratory exchange ratio: carbon dioxide production relative to oxygen consumption.
The athlete begins at low intensity. In this protocol, intensity rises every 3 minutes through progressive stages, according to the testing plan and appropriate stopping criteria.
Software uses the measurements and equations to estimate fat use at each intensity, showing where the highest rate occurs under the test conditions.
Fat Max data can be useful in two contexts:
First, when discussing fat-loss goals, it provides information about fuel use. But maximising fat oxidation during a workout does not automatically maximise long-term body-fat loss, which depends on overall energy balance and other factors.
Second, for long-distance athletes such as runners and cyclists, it can help a nutritionist understand fuel demands and plan food and race fuelling alongside training and other information.
For more on fat-loss strategies in cycling, here is a video with Diego Macaya from Tuvalum and me from INDYA – Sports Nutritionists explaining the test.
