There seems to be this idea that anyone who is a vegan is simply, by virtue of being vegan, going to be skinny and healthy and while I would say there is a much greater opportunity for this to be the case it isn't always and done incorrectly, veganism can result in you being just as much of a fat ass as people who eat across the spectrum.
I am not a vegan so I don't pretend to know all the answers but every now and then I meet an overweight vegan and I'm like "how TF did you manage that?"
My first instinct was to ask the guy how much fruit he consumes and lo' and behold, the answer was "a lot." He has fruit shakes constantly and fruit salads and will be working on some fruit as a snack basically all the time. Fruit is supposed to be good for you, right? Well, it is and it isn't. In doses fruit can be a wonderful thing for people who are craving something sweet but in too great a quantity it is actually one of the worst things for you.
This is especially true when it comes to fruit juices and in particular the mass produced ones.
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The big difference here is that there are no vitamins or anything good for you at all in the Coke but the juice obviously has these things. However, this doesn't mean that you should be chugalugging juice all day long and justifying it because of veganism. Many fruits are exceptionally high in sugar and calories, hence the awesome taste that they have. Just like for non vegans, fruits need to be consumed in moderation.
Potatoes are a big part of the problem for vegans. The fat vegans I know or even the fat vegetarians eat potatoes like there is no tomorrow and especially fried ones. Look man, just because you aren't eating meat doesn't mean that you can just deep fry everything and it somehow ends up being healthy. That is not the case at all and should be obvious.
A vegetable tempura is likely just as bad for you as fried chicken is. In fact, from a carbs standpoint, it is likely far worse.
Most vegetables, you can eat as much of it as you want and not have to worry about a thing but potatoes are an outlier and need to be eaten in moderation. They are calorie packed.
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Last off is fitness and how it can actually be more complicated for a vegan than for a non vegan because of one simple thing: Protein. Vegans have a difficult time getting a lot of protein and this is the fuel that your body needs after a workout. If you do not give your body enough protein it will cannibalize your own body and if you are not exercising, it will go for the muscle BEFORE it opts to "eat" the fat. This is a strange but true phenomenon that I don't fully understand I just know that it is the case.
Weight loss is 80% diet and 20% exercise but if you think that simply going vegan is going to mean that you don't have to regulate what kind of vegan foods you consume... you are simply dead wrong.
A fat vegan is a rarity, because it takes a certain amount of discipline that most people don't have to achieve that anyway but it can and does happen. Just because it comes from the earth doesn't mean you can have as much of it as you want and not gain weight. If that were the case I would change to veganism tomorrow and there would be an endless conveyer belt of fried stuff headed my direction.