It took some maths for me to figure out my own fat oxidation rate from my VO2max testing. Here’s the math (REE from VO2max).
At one point I got over 1.2 g/min of fat oxidation. Not bad considering that high numbers are often 1.6 g/min sort of numbers. Here’s the classical curve – an inverted parabola – of heart rate (x-axis) vs fat oxidation in g/min (y-axis).
The R^2 is 0.87 which is a pretty decent fit.
My sweet spot for maximum fat burning is about 120 bpm. My MAF range is 112-122 which nicely straddles this sweet spot of fat burning found during VO2max testing.
If you do the same maths on VO2max data you can find your sweet spot. But it won’t work well for fat burning if you are not fat adapted already. Or just use the MAF 180 formula.