I read a fantastic article on Mark’s Daily Apple today detailing certain foods etc and whether they “break” a fast (kicking you out of ketosis):

https://clicks.aweber.com/y/ct/?l=CV_1u&m=mU_ihseaJ6icE4Y&b=FOQoKImbT7aKLxK4KcmjDQ

I never new until now that Branch Chain Amino Acids (BCAAs – leucine, isoleucine, valine, and 2-aminoisobutyric acid) whether in concentrated tablet form or to a lesser degree in protein powders would break your fast!

I currently (on at least 5 days a week) have black coffee only in the morning and mid-morning, with an aim to fast for at least 16 hours with a secondary short fast between lunch and dinner. The reason I do this is I want all the benefits that fasting offers (including autophagy).