Although most states in the U.S. do not have laws protecting against this type of discrimination in the workplace, it is definitely worth discussing: weight discrimination. It's something that's extremely hard to prove and proving it would not bring much recourse anyway. But according to the deputy director of the Rudd Center for Food Policy and Obesity, there is research in the United States that shows that weight discrimination among women is "comparable to rates of racial discrimination." The director says weight discrimination has been documented as one of the most common types of employment discrimination that is experienced by individuals.
Lawsuits are unlike many aspects of most people's lives, unless they happen to be attorneys. While you may file a lawsuit on virtually any topic, you are unlikely to be successful if you cannot support your claims with valid evidence.