The most important thing for me about exercising is after doing so, your mindset is changed, it makes me want to eat healthy and not want to eat fast-food, it makes me start thinking about what im going to do the next day at the gym and fills me with motivation. If you get in to a routine of slouching around on your days off, all you will want is to be lazy and buy pre cooked meals and get deliveries.

Im a fan of intermittent fasting, and have been on it for a long time ( skip sometimes for social events) and do regular up to 20h fasts but for those of us that have been building up muscle and want to preserve as much as possible it is very hard to manage to eat around 1.8grams of protein per kg of weight in a small 4-6 hour eating window on a vegetarian/vegan diet. Its possible but its a lot of bulk of food. I avoid processed meats and follow a balanced diet and I think I am in good shape on the inside and outside! I hope I get to your age and have your motivation though, keep it up !