The rising number of Americans who are seriously overweight has triggered intense debate among scientists, advocacy groups, federal agencies, insurance companies and drug makers about whether obesity should be declared a "disease," a move that could open up insurance coverage to millions who need treatment for weight problems and could speed the approval of new diet drugs.

Proponents argue that new scientific understanding has clearly established that obesity is a discrete medical condition that independently affects health. Officially classifying obesity as a disease would have a profound impact by helping to destigmatize the condition, much as the classification of alcoholism as a disease made it easier for many alcoholics to get treatment, experts say.

But equally important, the move would immediately remove key economic and regulatory hurdles to prevention and treatment, they say.

Opponents contend that obesity is more akin to high cholesterol or cigarette smoking - a risk factor that predisposes someone to illness but is not an ailment in itself, such as lung cancer or heart disease.

Labeling it a bona fide disease would divert scarce resources, distract public health efforts from the most effective countermeasures and unnecessarily medicalize the condition, they say.

Nevertheless, the move to classify obesity as a disease appears to be accelerating. The Internal Revenue Service ruled last year that, for tax purposes, obesity is a disease, allowing Americans for the first time to claim a deduction for some health expenses related to obesity, just as they can for those related to heart disease, cancer, diabetes and other illnesses.

Weight-Control Therapies

The federal agency in charge of Medicaid and Medicare is conducting a review to determine whether it, too, should consider obesity a disease.

That would mean that for the first time the poor, elderly and infirm would be covered for some weight-control therapies without first having another illness diagnosed, such as diabetes. That decision would pressure private insurers to follow suit, and they are resisting the move.

Like thousands of others, Lori Asburry, 36, of Waldorf, Md., has been trying to get her insurance company to pay for a program she hopes will help her shed some of the 100 extra pounds she has been trying to lose.

"I think that insurance companies absolutely ought to cover this," Asburry said. "Some insurance companies now will pay for weight-loss surgery, which is a dramatic procedure. Yet they're not covering something that will have the same positive effects but in the end would end up saving them money."

At the same time, the Food and Drug Administration is reviewing how it judges new weight-loss drugs. As part of that review, the agency will consider whether it should evaluate diet drugs more like it assesses treatments for such illnesses as diabetes and cardiovascular disease, which could help get new medications on the market more quickly by making it easier to get them approved.

A Behavioral Issue

Together, these actions could result in a major shift in how the nation deals with what had long been considered a cosmetic or psychological problem, not a major public health crisis.

"For ages, obesity has been regarded as a personal moral failing - a behavioral issue that's easily fixed by people who have sufficient willpower to do so," said Morgan Downey, executive director of the American Obesity Association, a Washington-based advocacy group that has been lobbying for obesity to be reclassified.

"The modern scientific understanding of obesity is that it is a complex disease in its own right."

That understanding has led many major medical authorities, including the National Institutes of Health and the World Health Organization, to conclude that obesity should be considered a distinct disease entity.

"There's no question that obesity is a disease," said Arthur Frank, medical director of George Washington University's Weight Management Program. "Obesity is a disease where there's a disregulation of eating - just like diabetes is a disease where the system of controlling blood sugar is not functioning properly."

But not everyone agrees. Although obesity can increase the risk of a host of health problems, skeptics argue, so do smoking and high cholesterol, which are not considered diseases. Not everyone who is obese or overweight develops problems requiring treatment.

"You can be overweight and healthy if you are active," said Tim Church, medical director of the Cooper Institute in Dallas, a nonprofit research center focused on exercise. "In fact, an overweight individual who exercises is healthier than a normal-weight individual who is sedentary. You could say that if obesity is a disease, then not enough exercise is a disease or not eating right is a disease."

Then there is the fact that being overweight can actually have some health benefits, said Paul Ernsberger, an associate professor of nutrition at Case Western Reserve University School of Medicine in Cleveland.

"When something is a disease it doesn't have beneficial or neutral effects. There's a decreased incidence of osteoporosis in older people who are overweight. Where some cancers are increased, there are others that are decreased. So calling it a disease is misleading," said Ernsberger, a scientific adviser to the National Association to Advance Fat Acceptance.

Nonetheless, the IRS, under pressure from the American Obesity Association, declared obesity a disease in April 2002. That allows taxpayers to deduct the cost of weight-loss treatments prescribed by a doctor, including such programs as Weight Watchers that insurance does not cover. Previously, such costs could be deducted only if prescribed by a doctor to treat another condition, such as hypertension.

But most health insurance programs, including the federal Medicaid and Medicare programs, do not cover such costs. As a result, people often cannot be reimbursed for diet programs, nutritional counseling or drugs unless they have a condition that is considered a disease, such as diabetes or heart disease. Parents of overweight or obese children similarly cannot get treatment that may prevent them from developing health problems later in life.

Obesity Treated With Disdain

Eugene V. Martin, 67, of the District has not been able to get his insurance company to pay for one of the few available prescription weight-loss drugs.

"Both the medical profession and the insurance industry seem to treat obesity with such disdain and abhorrence instead of assistance and support," he said. "It certainly isn't rational, and I think goes back to the general sense that we're fat because we simply can't control ourselves."

The insurance industry, however, argues that it is more appropriate for employers to pay for such services through employee assistance programs, and many already do. In addition, the effectiveness of many weight loss programs, on which Americans spend almost $40 billion a year, remains far from clear.

"There is a growing sense that perhaps Americans are too heavy, but I think there's also an awareness that there's not a single solution to address the problem," said Larry Akey, a spokesman for the Health Insurance Association of America.

"It's really going to require a whole host of responses, and not simply, 'Let's have the insurance companies pay for it.' There is a line that sometimes get blurred between legitimate health care expenditures and lifestyle or behavioral changes."

Nevertheless, the agency that runs the federal Medicare and Medicaid programs is studying whether to classify obesity as a disease, and, if so, what types of treatment have been demonstrated to be effective. The Agency for Health Care Research and Quality delivered a report outlining the evidence on both sides of the debate in September, and a decision is expected any time.

"We certainly recognize and agree that obesity is a significant problem. The question is whether losing weight, which people can do without ever seeing a provider, is something a health care system ought to pay for," said Steve Phurrough, director of the coverage and analysis group at the Centers for Medicare and Medicaid, which will make the decision.

If obesity is classified as a disease, then the question will become precisely what types of treatment should be covered, he said.

"For example, if it's demonstrated that exercise is beneficial for obesity, there could be an argument that Medicare ought to buy a Gold's Gym membership," Phurrough said. "Another issue is diet counseling. One of the difficulties is that I'm not sure there's a lot of medical evidence that going to see a dietician actually helps people lose weight."

Meanwhile, FDA officials met with drug companies and the American Obesity Association in April and will gather again, perhaps as soon as this month, to discuss whether obesity drugs should continue to be held to tougher safety and efficacy standards than those for diseases such as diabetes.

"There is a fair bit of consensus in the field that the FDA has been somewhat hostile to obesity products and don't treat it like cancer and other major diseases," said Downey, of the Obesity Association.

The growing recognition that obesity is a major public health problem has prompted the FDA to begin a review that is likely to result in revised guidelines for testing diet drugs, FDA Commissioner Mark McClellan said.

"There's certainly a careful evaluation going on right now to make sure we're using the most efficient and effective approach for reviewing weight-loss therapies," he said. "This is an important enough problem . . . that we want to make sure our regulatory process is up to date as possible. We really need those treatments."

Advocates hope that taken together these moves could push more people to seek help for obesity by making it less of a personal failing and more of a medical condition.

"There are a lot of people who believe obesity is a simple failure of willpower," said Richard L. Atkinson Jr. of the University of Wisconsin at Madison, president of the American Obesity Association. "In my mind, there's no doubt whatsoever that obesity is a disease. If diabetes is a disease, if heart disease is a disease, then obesity is a disease."