Well most of us here find eating the higher fats, keeps us satisfied for much longer, so of course eat less.
What are your fat sources?
Starvation mode is a CW thing, when you are actually starving and not eating.
Not sure on PCOS and fasting, but fasting I feel great.
But I would not attempt to try until fully fat adapted, or you will probably get hungry and not feel great.
I tried it last year, but was not ready and it made me binge.
I am up to nearly 40 hours of a half fast (bulletproof coffee and bone broth only) and I still feel good. Hopefully someone will PCOS will answer this for you soon.