I am not exactly sure how to explain this method, but it is not so much that I gain weight on this lifestyle, as much as because of the water density of the food my digestion is changed by it resulting in net water weight gain and sometimes I think my body can't catch up (though really I am just speculating)
Recently I have decided to space my meals differently, so that there is a larger period of time between meals, and that the meals I do have are larger. Previously I was going from 2-3 fruit meals consisting of about 500-1000 calories a piece, with the addition of a low fat cooked vegan meal in the evening at home with salad or sometimes social vegan meals at other places (salt, fat yikes).
I have changed the above system to 2 meals a day, 1 fruit meal consisting of 2000 calories or more in one sitting (yes it does take longer to complete this meal!!!) And it is 9 times out a 10 mono, where as before I was having 2-3 different fruits a day. My second meal is what I said before, low fat cooked vegan with salad or a social vegan meal, though I have been having considerably less of those and forcing my friends to do things other than eat when we hang out.
I gotta say my weight was fairly stable, not going up or down doing what I was doing before, though I saw lots of other improvements from being relatively low fat and definitely high carb, the weight was not budging much. This new way of doing things, even though I am eating the same amount of calories and nutrition, is making the weight just fall off. I swear every morning I wake up my stomach is flatter and my body less floppy. Which I swear must be a weird water weight thing that I dont get. The new eating pattern is also making me stop eating earlier in the day which is probably a huge factor.
Either way I am pleased with what is happening. So maybe if you think that you gain weight on this lifestyle, or are just stuck at your weight like I was, maybe it is something with your meal timing. I dont really know for sure, I just know what seems to work for me! Looking forward to posting some new after pics after some months doing it this way!