Yeah, there are a lot of sources out there on this subject. It generally takes 10-14 days for your body to adjust to burning fat instead of storing excess sugar. People also tend to be hangry and have bad headaches during the transition. IF can be helpful to keep your body from returning to the sugar rollercoaster. The problem is our food supply is built on cheap sugar/corn. It takes focused and deliberate effort to change. Most people have too much stress in their lives already and this is just not sustainable for them.