Marilyn Wann is an author and weight diversity speaker in Northern California who has a message for anyone making judgments about her health based on her large physique. “The only thing anyone can accurately diagnose by looking at a fat person is their own level of stereotype and prejudice about fat,” said Ms. Wann, a 43-year-old San Franciscan whose motto in life is also the title of her book: “Fat! So?”

Hers has been an oft-repeated message this summer and fall by members of the “fat pride” community, given that the nation is in the midst of a debate about health care. That debate has, sometimes awkwardly, focused its attention on the growing population of overweight and obese Americans with unambiguous overtones: fat people should lose weight, for the good of us all.

Heavier Americans are pushing back now with newfound vigor in the policy debate, lobbying legislators and trying to move public opinion to recognize their point of view: that thin does not necessarily equal fit, and that people can be healthy at any size.

Extra weight brings with it an increased risk of chronic disease, medical experts say, and heavier people tend to have medical costs that are substantially higher than their leaner counterparts. As a result, Congress is considering proposals in the effort to overhaul health care that would make it easier for employers to use financial rewards or penalties to promote healthy behavior by employees, like weight loss.