I've been intermittent fasting since 2014. On most days I go from 11 AM to 11 AM the next day, which is OMAD (one meal a day). It took me a while to get there. I originally did an 8 hour eating window with 16 hours of fasting and struggled. Now I can fast no problem and the longest I've gone is 60 hours a few different times, and I trained Brazilian Jiu Jitsu twice during those times, as in both fasted days. The key is I put a little pink salt or Redmond Real Salt into my water to always have electrolytes. Another key is the food you eat when re-feeding can cause blood sugar issues which will lead to hunger. I'm referring to carbs. To fast without blood sugar issues the easiest way is keto/carnivore as the protein will keep you full and your body will burn the fat for energy. These days I eat coconut oil, meat, seafood, eggs, and olives. Works like a charm.