The most common cause of health issues these days tends to be due to excessive weight. If a person was penalized for being a certain weight, the overall effect would be positive. There would be less hospitalization due to heart issues as well as create an environment that focuses on longer life spans.
No, there should not be a maximum weight law, because people have a right to eat themselves to an unhealthy weight if they want to. It is unfair to control people to the level that we control what they eat. People can do other things that are not good for them, like smoking cigarettes. They should eat what they want, too.