That means you are pushing your limits. Don't start with a full day fasting. Start slow by doing some form of intermittent fasting or time restricted feeding. I would say go for having early dinner and a late breakfast to begin with. Once you are adapted to log hours of not eating, skip one of the meals in the day, depends on your situation but the easiest one to start with is skipping breakfast. Then you can slowly work your way to full day fasting.