I think it's almost a given that they're not. Just staying vegetarian if you eat a lot of processed foods will involve quite a bit of extra care. And so much more so if one wants to be vegan. Calorie counting is child's play in comparison to keeping track of which foods you'd think are vegan actually aren't. Even if they're not having "cheat meals" or something I doubt most of them really are keeping vegan. And just in general I'm willing to bet a pretty good chunk of fat vegans are still gobbling down cheese on a regular basis behind closed doors.