Hiit and fat fast

What kind of anaerobic training is better suited when doing fat fast or low calorie keto,short brutal intervals (active time to rest ratio 1:1/2)or intense but prolonged 1:3 Ratio?Since there should be a shortage of glycogen the briefer ones seem to be the choice to me,but I wondered if the higher intensity could stress the system too much and lead to catabolism.Could you give me any guess/Clear my doubts please?
Thank you

Best way to approach fat fast is to use the energy systems that are still working well. The phosphocreatine system should not be significantly compromised so lift very heavy with low volume. But the phosphocreatine system needs carbs to replenish correctly, so I’d rather use this system to supply energy during my lifting workouts rather than HIIT.

Moderate intensity cardio is a better choice for a no carb diet because you can easily use the correct energy substrates during this type of exercise.

Carbs are a must for HIIT and high volume training and these should be avoided while on a fat fast type of plan.