You should become keto-adapted first. That is, your body should be able to switch back and forth between using fat for energy and glycogen for energy. If you've been eating a typical diet, you aren't adapted to using fat for energy. You will feel weak and hungry, even dizzy or faint, if you go without eating for a long time. Give your body a chance to switch itself over to a more flexible energy-burning system. Then if you use IF, it will be painless. In fact, it's when you can go a day without eating with no suffering and even feeling great that you'll know you are adapted. And once you're adapted, your body will be able to use its own fat stores for energy while you fast, and you'll feel energetic and strong, not weak.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 170 x 3. Current Deadlift: 220 x 3