WASHINGTON, Nov. 15— If the usual rigors of serving in Congress were not enough, Representative Jerrold Nadler, a Manhattan Democrat, struggled for years with the personal torment of being so overweight that he could not make it up even a single flight of stairs to the second floor of the Capitol to vote on the House floor. He used the elevator instead.
''I can't tell you how many people -- complete strangers -- have come up to me and said, 'Congressman, you're doing a great job, and I want you to continue to be my congressman, so you have to lose weight,' '' he said in an interview. ''Imagine how that makes you feel.''
Now, after decades of health-threatening obesity and futile dieting, Mr. Nadler has taken a more aggressive course: During the Congressional recess in early August, he underwent stomach-reduction surgery at Mount Sinai Hospital in Manhattan, following in the steps of a small but rising number of overweight people, most recently (and famously) Al Roker, the weatherman for NBC's ''Today'' program.
Mr. Nadler peaked at 338 pounds before the surgery, whereas Mr. Roker peaked at 320 pounds. But Mr. Roker is 5 feet, 8 inches tall, while Mr. Nadler is 5-foot-4. Mr. Nadler was so obese that he long ago gave up riding the subway in New York to avoid the tiring climb up and down the steps.
Mr. Nadler, an influential New York politician who became known nationally for his staunch defense of President Clinton, said he took this radical step after realizing that his life depended on it. ''I want to live to see my grandchildren grow up,'' he said. ''How many grossly overweight 80-year-olds do you know?''
The results have been striking: Mr. Nadler, who is 55, has shed 61 pounds -- and taken in his suits three times. He even surprised himself the other day when he walked the 40 blocks or so from his district office in Lower Manhattan to Penn Station. In the past, he avoided walking even a few blocks.
Since the operation, Mr. Nadler said, he has had to change his eating habits drastically because he feels terribly uncomfortable if he eats too much. In the past, he would typically consume a salad, a bowl of onion soup, a 14-ounce rib-eye steak with french fries, vegetables, bread and butter and a dessert -- all washed down with diet Coke. He also snacked constantly -- on Oreo cookies, Fig Newtons, frankfurters and even tuna salad and chicken salad sandwiches.
''I'd be constantly noshing in the cloakroom,'' he said.
These days, Mr. Nadler will order a four-ounce steak sandwich, discard the Kaiser roll and eat only three quarters of the meat. (He will have vegetables only if he has room -- and he skips dessert and has nothing to drink.) He has also stopped snacking. ''Snacks are out,'' he said. ''What I do now is munch on ice cubes.''
Mr. Nadler, who has served in the House for nearly 10 years, is also trying to be more active and less sedentary. His usual breakfast, a tuna fish or chicken salad sandwich with tomatoes and mayonnaise, is now entirely out of the question.
People have already started to notice the difference in the congressman, who has frequently been the butt of cruel humor, even among those who respect his formidable intellect and sharp political instincts. (In 1998, for example, when Alfonse M. D'Amato was a senator from New York, he referred to Mr. Nadler as ''Jerry Waddler'' in a private meeting of politicians, a remark that later became public.)
Mr. Nadler said that while he has publicly shrugged off such incidents he was, in fact, wounded by them. ''You try to ignore it,'' he said. ''But, of course, it's hurtful. I've learned to laugh it off. But it's hurtful.''
Mr. Nadler decided to talk to a reporter about his operation because, his aides said, he believed it would be only a matter of time before people started asking questions.
''I thought it should be publicized,'' he said. ''But I wanted it done responsibly. I didn't want it ending up in The National Enquirer.''
The surgery that Mr. Nadler underwent is becoming increasingly popular, at a time when diet, exercise and weight-loss drugs have failed to counter the rising tide of obesity in America. From 1999 to 2000, 64.5 percent of American adults were overweight, according to a recent study published by The Journal of the American Medical Association, with 35.2 percent qualifying as obese or morbidly obese.
As a result, medical experts now regard obesity as one of the worst public health problems in the nation. It greatly increases the risk of illnesses that are among the leading causes of death, including diabetes, heart disease, respiratory problems and some forms of cancer.
There are many theories for the weight gain in the United States -- from a lack of exercise to the proliferation of fast food. But whatever the cause, medical experts agree that for most obese patients, there is little long-lasting success in dieting, exercise or weight-loss drugs.
Mr. Nadler -- who is partial to a genetics theory since his identical twin brother is also obese -- said he had tried every conceivable way to lose weight. Routine exercise. Liquid diets. Weight Watchers. A month-long stay at the Duke University weight loss center in Durham, N.C. And even fen-phen, the popular diet pill combination linked to problems with heart valves. But nothing seemed to work.
The surgery is not a quick or easy cure. It is as painful and as risky as any major abdominal operation. It forces people to make big changes in the way they eat, makes them extremely ill or terribly uncomfortable if they eat too much and puts them at risk for nutritional deficiencies.
But it is highly effective. No drug or diet has led to the large and lasting weight loss that the surgery has helped most patients achieve, according to medical experts. In many cases, people lose 100 pounds.
It is expensive, typically costing more than $20,000, although it is often covered by insurance.
''It's not a risk I took lightly,'' Mr. Nadler said of the stomach surgery, citing statistics showing that 1 out of 200 people die as a result of the procedure. ''But on the other hand, I've been struggling with weight all my life. It's frustrating.''
In the United States, the number of bariatric operations, as the surgical procedure is known among medical experts, tripled to 60,000 annually in 2002, from 20,000 in 1995, according to statistics from the American Society of Bariatric Surgery.
By the time Mr. Nadler decided to have the procedure done, his health had already deteriorated considerably. ''He was already very sick when we saw him,'' said Dr. Michel Gagner, his surgeon. ''He had multiple diseases from his obesity.''
Dr. Gagner said the procedure Mr. Nadler underwent is a variation of a more common stomach operation performed in the United States.
The more common procedure involves stapling shut most of the stomach and creating a small, one-ounce pouch severely restricting how much food a patient can eat. Then the upper portion of the small intestine is bypassed to reduce the calories the body absorbs.
The operation Mr. Nadler had simply narrows the stomach into a ''sleeve'' that can take as much as three ounces of food. The sleeve is then connected to the lower half of the small intestine, for the reduction of calories the body absorbs.
Dr. Gagner said that the procedure offers ''super obese'' patients a better chance of taking off large amounts of weight and keeping it off.
In the end, Mr. Nadler said, what convinced him to undergo surgery was some gentle prodding from his wife, Joyce L. Miller, who pulled information about the operation off the Internet, as well as the advice of a friend who had had the surgery.
Now, he's hoping to reach his ideal weight, about 160 pounds. ''I was extremely, morbidly obese,'' he said, referring to himself before the surgery. ''Now I'm only morbidly obese. I'm getting there.''