Sometimes when I discuss my diet with others, they will point out to me a vegan they may know who might be considered obese. Just because a food or beverage is vegan doesn’t mean it’s not junk food. Take high-fructose corn syrup. High levels of fructose in the diet has been shown to be very hard on the liver and a major cause of obesity. People only consume around 15 grams of fructose from eating several pieces of fruit a day while a single can of regular American soda contains 23 grams. (Note that many sodas in other countries still use cane sugar which is actually somewhat healthier for you — and taste better according to this author!)
Of course, sugar substitutes and excess fats (usually in the form of deep-fried foods like french fries) should be avoided also.