Ofc not everyone who live in a capitalist system is fat.
What capitalism does is allowing an environment where people can make money from actually harming other people's health. Tobacco and alcohol are some examples. Candy is another example, and so is unhealthy fast food like Mc Donald's. The more food people eat, the more the food-producing corporations benefit, so it's not a surprise they will do everything they can to make people eat as much as possible, also more than they need, or even unhealthy food which we don't need at all.
Every single person working on a Coca Cola factory or at Mc Donald's would do more good to society simply by being unemployed.
Also I don't see any reason to make fun of fat people. At least I don't think it's fun.