Metabolism question?

Why does it seem like when i lean out It's easier for me to stay lean... I mean after cutting 30 lbs and going below 10% BF I notice that my BF doesn't go over 10% very easy.. I hardly diet anymore, I mean for the most part I eat what ever.  Could your metabolism speed up when your BF% decreases to a certain point?   What are your thoughts?  Can you explain why this is happening? 

Lots of possible reasons for this.

Fat acts as a gland and communicates about maintaining fat levels.

Also, our body had weight monitoring processes.  If it likes the weight you are at, it makes it very hard to change because it modulates the metabolism to maintain it.

Another point, if you have been burning fat, the fat mobilizing and burning mechanisms are upregulated and so you enjoy a period of very efficient fat metabolism.

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