Hey I’m new to IF so take that for what it is. I’m vegan as well, but oh lord I have been a junk food vegan for years. So I’m starting If and I’m cutting out all the sugars first but keeping the mock meats. I’m also cooking a lot of protein heavy stews, like lentil soup but double the lentils. And I serve it over whole grains like barley or farro, stuff that fills you up. Also heavy of the cruciferous veggies and of course tofu. R/plantbaseddiet will be a good spot to check out.
As for the swimming. I love swimming but I find that it makes me super hungry. If it’s an issue start slow and maybe walk or do mild cardi on an elliptical instead. I own an exercise bike and I’m using that.
In any case, start on the diet and adjust the exercise to what you can handle and not importantly: maintain.