I've had a similar experience but with low carb. I eat two meals, one extremely low carb, and one "normal" meal for lunch and dinner and do the 16/8 plan. Have dropped 42lbs in 4 months. I have much better mental clarity and more energy, and cut way back on caffeine as a result. I could never do a vegan diet because it goes against my personal research as to what humans should be eating, but I think that IF can be used for any reasonable diet (caloric restriction) plan.