The metabolic feedback loop there is not precise as you may think. There is a huge variability and even big thresholds of when it starts switching. That's why y

The metabolic feedback loop there is not precise as you may think. There is a huge variability and even big thresholds of when it starts switching. That's why you need to measure your calories intake and results, and act accordingly. Small calories deficit won't slow down the metabolism, especially if you add a bit of excercise or physical activity to the list. Big calories deficit on the other hand could cause issues.