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.

Other less-scientific arguments have also gained traction on blogs, chat shows and editorial pages since talk of the overhaul began in earnest, with the overweight cast as lazy or gluttonous liabilities and therefore not entitled to universal health coverage because of poor personal decision-making. As that thinking goes, a healthful eater should not have to pay for the consequences of someone else’s greasy burger binges.

Either way, heavy people — characterized as over-consumers of health care or as those who should miss out on discounts because of their size — say they have been maligned throughout the debate.

“I thought, ‘Health reform? Yay!’ ” said Lynn McAfee, the director of medical advocacy for the Council on Size and Weight Discrimination, an advocacy group for heavy people. But Ms. McAfee said it was not long before her sentiment changed to the more sober, “Oh no, we’re being scapegoated again.”

It is an uphill battle. But the health care debate has, unexpectedly, also provided an opportunity for new expressions of what Ms. Wann calls “fat pride,” the notion that weight diversity is a good thing and that size discrimination is as offensive as any other kind.

“The stigma is so heavy a burden that it took our community 40 years before it could go to Capitol Hill and lobby for ourselves,” said Ms. Wann, a member of the National Association to Advance Fat Acceptance , an advocacy group that organized a lobbying trip to Washington for its members this spring. “We’re kind of a popular punching bag. You can do incredibly discriminating, hurtful, hateful things to fat people in public and not only get away with it but be seen as some kind of superhero.”

On Capitol Hill, the association asked legislators for a public option from which fat people could not be excluded because of weight and for coverage that did not consider excess weight a pre-existing condition.

“Basically,” Ms. Wann continued, “we want to be treated with respect the same as everyone else.”

Americans are more overweight and obese than they were 10 years ago, or even one year ago, according to the Robert Wood Johnson Foundation and the Trust for America’s Health , which published a state-by-state study in June.

It showed that the trend is up sharply.

Two-thirds of all Americans are overweight or obese. In four states — Alabama, Mississippi, Tennessee and West Virginia — more than 30 percent of adults are obese. In 1991, in contrast, no state had an obesity rate over 20 percent.

And, according to the American Obesity Association, a research organization, poor minority women have the greatest likelihood of being overweight.

Weight is an incendiary issue, experts said, and that may be why it had such staying power as a hot topic of conversation through the health care debate.

“All national health insurance systems are built on the idea that we’re all part of a community, we all get sick and die, so we’re going to take care of one another,” said James Morone, a professor of political science and urban studies at Brown University . “The best philosophical way to stop national health insurance is to say we’re not a community, it’s ‘us vs. them.’ ”

But what has been different about this particular issue, this year, is that “people are pushing back,” Professor Morone said.

Peggy Howell, the public relations director for the National Association to Advance Fat Acceptance, said she had been on the phone delivering her group’s message and answering more news media calls this year than ever before.

The message is simple, she said: “We believe that fat people can eat healthy food and add movement to their lives and be healthy. And healthy should be the goal, not thin.”

That idea is gaining strength and popularity among a segment of the overweight population that feels as though traditional dieting to lose weight does more harm than good, ultimately benefiting the $30 billion weight loss industry, not the public.

“I get so angry when I feel people pushing a weight-loss agenda,” said Linda Bacon, a nutrition professor at City College of San Francisco and author of “Health at Every Size,” a book published last year whose title has become the rallying cry of the fat pride community. “What we’re doing in public health care policy is harmful. We give a direct and clear message that there’s something wrong with being fat.”

A federally financed study by Ms. Bacon, published in the book, found that there were many people who could be healthy in fat bodies.

Ms. Wann used some of Ms. Bacon’s findings as her talking points when she visited legislators with other lobbyists for “fat acceptance” in May.

She said she felt encouraged that the health care bill the House Democratic leaders unveiled on Thursday does not allow changes in insurance pricing based on obesity. But there is still a long way to go before any bill becomes law.

“For me, the takeaway point that was heartening and historic and exhilarating is that it was the first time we started lobbying for a humane health-enhancing system,” said Ms. Wann, who is self-employed and, in her own words, fat and uninsurable.

“We’re all in this life raft together,” she said.