At 7:30 A.M. on September 13, 1999, an anesthesiologist and two orderlies rolled our patient, whom I will call Vincent Caselli, into the operating room, where his attending surgeon and I awaited him. Caselli was a short man of middle age-five feet seven, fifty-four years old. The son of Italian immigrants, he had worked as a heavy-machine operator and road-construction contractor. (He and his men had paved a rotary in my own neighborhood.) He had been married for thirty-five years; he and his wife had three girls, all grown now. And he weighed four hundred and twenty-eight pounds. Housebound, his health failing, he no longer had anything resembling a normal life. And so, although he was afraid of surgery, he had come for a Roux-en-Y gastric-bypass operation. It is the most drastic treatment we have for obesity. It is also among the strangest operations surgeons perform. It removes no disease, repairs no defect or injury. It is an operation that is intended to control a person's will-to manipulate his innards so that he does not overeat-and it is soaring in popularity. Some forty-five thousand patients underwent obesity surgery in 1999, and the number is expected to double by 2003.



For the very obese, general anesthesia alone is a dangerous undertaking; major abdominal surgery can easily become a disaster. Obesity substantially increases the risk of respiratory failure, heart attacks, wound infections, hernias-almost every complication possible, including death. Nevertheless, Dr. Sheldon Randall, the attending surgeon, was relaxed, having done more than a thousand of these operations. I, the assisting resident, remained anxious. Watching Caselli struggle to shift himself from the stretcher onto the operating table and then stop halfway to catch his breath, I was afraid that he would fall in between. Once he was on the table, his haunches rolled off the sides, and I double-checked the padding that protected him from the table's sharp edges. He was naked except for his "universal"-size johnny, which covered him like a napkin, and a nurse put a blanket over his lower body for the sake of modesty. When we tried to lay him down, he lost his breath and started to turn blue, and the anesthesiologist had to put him to sleep sitting up. Only with the breathing tube and a mechanical ventilator in place were we able to lay him flat.

He was a mountain on the table. I am six feet two, but even with the table as low as it goes I had to stand on a step stool; Dr. Randall stood on two stools stacked together. He nodded to me, and I cut down the middle of our patient's belly, through skin and then dense inches of glistening yellow fat, and we opened the abdomen. Inside, his liver was streaked with fat, too, and his bowel was covered by a thick apron of it, but his stomach looked ordinary-a smooth, grayish-pink bag the size of two fists. We put metal retractors in place to hold the wound open and keep the liver and the slithering loops of bowel out of the way. Working elbow deep, we stapled his stomach down to the size of an ounce. Before the operation, it could accommodate a quart of food and drink; now it would hold no more than a shot glass. We then sewed the opening of this little pouch to a portion of bowel two feet past his duodenum-past the initial portion of the small bowel, where bile and pancreatic juices break food down. This was the bypass part of the operation, and it meant that what food the stomach could accommodate would be less readily absorbed.

The operation took us a little over two hours. Caselli was stable throughout, but his recovery was difficult. Patients are usually ready to go home three days after surgery; it was two days before Caselli even knew where he was. His kidneys failed for twenty-four hours, and fluid built up in his lungs. He became delirious, seeing things on the walls, pulling off hisoxygen mask, his chest leads for the monitors, even yanking out the I.V. We were worried, and his wife and daughters were terrified, but gradually he pulled through.

By the third day after surgery, he was well enough to take sips of clear liquids (water, apple juice, ginger ale), up to one ounce every four hours. On my afternoon rounds, I asked him how he'd done. "O.K.," he said. We began giving him four-ounce servings of Carnation Instant Breakfast for protein and modest calories. He could finish only half, and that took him an hour. It filled him up and, when it did, he felt a sharp, unpleasant pain. This was to be expected, Dr. Randall told him. It would be a few days before he was ready for solid food. But he was doing well. He no longer needed I.V. fluids. And, after he'd had a short stay in a rehabilitation facility, we sent him home.

A couple of weeks later, I asked Dr. Randall how Caselli was getting on. "Just fine," the surgeon said. Although I had done a few of these cases with him, I had not seen how the patients progressed afterward. Would he really lose all that weight? I asked. And how much could he eat? Randall suggested that I see Caselli for myself. So one day that October, I gave him a call, and he invited me to stop by.

Vincent Caselli and his wife live in an unassuming saltbox house not far outside Boston. To get there, I took Route 1, past four Dunkin' Donuts, four pizzerias, three steak houses, two McDonald's, two Ground Rounds, a Taco Bell, a Friendly's, and an International House of Pancakes. (A familiar roadside vista, but that day it seemed a sad tour of our self-destructiveness.) I rang the doorbell, and a long minute passed. I heard a slow footfall coming toward the door, and Caselli, visibly winded, opened it. But he smiled broadly when he saw me and gave my hand a warm squeeze. He led me-his hand on table, wall, doorjamb for support-to a seat at a breakfast table in his flowered-wallpaper kitchen.

I asked him how things were going. "Real good," he said. He had no more pain from the operation, the incision had healed, and, though it had been only three weeks, he'd already lost forty pounds. But, at three hundred and ninety, and still stretching his size-64 slacks and size-XXXXXXL T-shirts (the largest he could find at the local big-and-tall store), he did not yet feel different. Sitting, he had to keep his legs apart to let his abdomen sag between them, and the weight of his body on the wooden chair forced him to shift every minute or two because his buttocks would fall asleep. Sweat rimmed the folds of his forehead and made his thin salt-and-pepper hair stick to his pate. His brown eyes were rheumy, above dark bags. He breathed with a disconcerting wheeze.

We talked about his arrival home from the hospital. The first solid food he had tried was a spoonful of scrambled eggs. Just that much, he said, made him so full it hurt, "like something was ripping," and he threw it up. He was afraid that nothing solid would ever go down. But he gradually found that he could tolerate small amounts of soft foods-mashed potatoes, macaroni, even chicken if it was finely chopped and moist. Breads and dry meats, he found, got "stuck," and he'd have to put a finger down his throat and make himself vomit.

Caselli's battle with obesity, he explained, began in his late twenties. "I always had some weight on me," he said-he was two hundred pounds at nineteen, when he married Teresa (as I'll call her), and a decade later he reached three hundred. He would diet and lose seventy-five pounds, then put a hundred back on. By 1985, he weighed four hundred pounds. On one diet, he got down to a hundred and ninety, but he gained it all back. "I must have gained and lost a thousand pounds," he told me. He developed high blood pressure, high cholesterol, and diabetes. His knees and his back ached all the time, and he had limited mobility. He used to get season tickets to Boston Bruins games, and go out regularly to the track at Seekonk every summer to see the auto racing. Years ago, he drove in races himself. Now he could barely walk to his pickup truck. He hadn't been on an airplane since 1983, and it had been two years since he had been to the second floor of his own house, because he couldn't negotiate the stairs. "Teresa bought a computer a year ago for her office upstairs, and I've never seen it," he told me. He had to move out of their bedroom, upstairs, to a small room off the kitchen. Unable to lie down, he had slept in a recliner ever since. Even so, he could doze only in snatches, because of sleep apnea, which is a common syndrome among the obese and is thought to be related to excessive fat in the tongue and in the soft tissues of the upper airway. Every thirty minutes, his breathing would stop, and he'd wake up asphyxiating. He was perpetually exhausted.

There were other troubles, too, the kind that few people speak about. Good hygiene, he said, was nearly impossible. He could no longer stand up to urinate, and after moving his bowels he often had to shower in order to get clean. Skin folds would become chafed and red, and sometimes develop boils and infections. And, he reported, "Sex life is nonexistent. I have real hopes for it." For him, though, the worst part was his diminishing ability to earn a livelihood.

Vincent Caselli's father had come to Boston from Italy in 1914 to work in construction, and he soon established his own firm. In 1979, Vincent went into business for himself. He was skilled at operating heavy equipment-his specialty was running a Gradall, a thirty-ton, three-hundred-thousand-dollar hydraulic excavator-and he employed a team of men year-round to build roads and sidewalks. Eventually, he owned his own Gradall, a ten-wheel Mack dump truck, a backhoe, and a fleet of pickup trucks. But in the past three years he had becometoo big to operate the Gradall or keep up with the daily maintenance of the equipment. He had to run the business from his house, and pay others to do the heavy work; he enlisted a nephew to help manage the men and the contracts. Expenses rose, and since he could no longer go around to city halls himself, he found contracts harder to get. If Teresa hadn't had a job-she is the business manager for an assisted-living facility in Boston-they would have gone bankrupt.

Teresa, a freckled redhead, had been pushing him for a long time to diet and exercise. He, too, wanted desperately to lose weight, but the task of controlling himself, day to day, meal to meal, seemed beyond him. "I'm a man of habits," he told me. "I'm very prone to habits." And eating, he said, was his worst habit. But, then, eating is everyone's habit. What was different about his habit? I asked. Well, the portions he took were too big, and he could never leave a crumb on his plate. If there was pasta left in the pot, he'd eat that, too. But why, I wanted to know. Was it that he just loved food? He pondered this question for a moment. It wasn't love, he decided. "Eating felt good instantaneously," he said, "but it only felt good instantaneously." Was it excessive hunger that drove him? "I was never hungry," he said.

As far as I could tell, Caselli ate for the same reasons that everyone eats: because food tasted good, because it was seven o'clock and time for dinner, because a nice meal had been set out on the table. And he stopped eating for the same reason everyone stops: because he was full and eating was no longer pleasurable. The main difference seemed to be that it took an unusual quantity of food to make him full. (He could eat a large pizza as if it were a canape.) To lose weight, he faced the same difficult task that every dieter faces-to stop eating before he felt full, while the food still tasted good, and to exercise. These were things that he could do for a little while, and, with some reminding and coaching, for perhaps a bit longer, but they were not, he had found, things that he could do for long. "I am not strong," he said.

In the spring of 1999, Caselli developed serious infections in both legs: as his weight increased, and varicosities appeared, the skin thinned and broke down, producing open, purulent ulcers. Despite fevers and searing pain, it was only after persistent coaxing from his wife that he finally agreed to see his doctor. The doctor diagnosed a serious case of cellulitis, and he spent a week in the hospital receiving intravenous antibiotics.

At the hospital, he was given an ultrasound scan to check whether blood clots had formed in the deep veins of his legs. A radiologist came to give him the results. Caselli recounted the conversation to me. "He says, 'You don't have blood clots, and I'm really surprised. A guy like you, in the situation you're in, the odds are you're gonna have blood clots. That tells me you're a pretty healthy guy' "-but only, he went on, if Caselli did something about his weight. A little later, the infectious-disease specialist came by to inspect his wounds. "I'm going to tell you something," Caselli recalls the man saying. "I've been reading your whole file-where you were, what you were, how you were. You take that weight off-and I'm not telling you this to bust your ass-you take that weight off and you're a very healthy guy. Your heart is good. Your lungs are good. You're strong."

"I took that seriously," Caselli said. "You know, there are two different doctors telling me this. They don't know me other than what they're reading from their records. They had no reason to tell me this. But they knew the weight was a problem. And if I could get it down somewhere near reality . . ."

When he got home, he remained sick in bed for another two weeks. Meanwhile, his business collapsed. Contracts stopped coming in entirely, and he knew that when his men finished the existing jobs he would have to let them go. Months before, his internist had suggested that he consider surgery and he had dismissed the notion. But he didn't now. He went to see Dr. Randall, who spoke with him frankly about the risks involved.There was a one-in-two-hundred chance of death and a one-in-ten chance of a significant complication, such as bleeding, infection, gastric ulceration, blood clots, or leakage into the abdomen. The doctor also told him that it would change how he ate forever. Unable to work, humiliated, ill, and in pain, Vincent Caselli decided that surgery was his only hope.

It is hard to contemplate the human appetite without wondering if we have any say over our lives at all.We believe in will-in the notion that we have a choice over such simple matters as whether to sit still or stand up, to talk or not talk, to have a slice of pie or not. Yet very few people, whether heavy or slim, can voluntarily reduce their weight for long. The history of weight-loss treatment is one of nearly unremitting failure. Whatever the regimen-liquid diets, high-protein diets, or grapefruit diets, the Zone, Atkins, or Dean Ornish diet-people lose weight quite readily, but they do not keep it off. A 1993 National Institutes of Health expert panel reviewed decades of diet studies and found that between ninety and ninety-five per cent of people regained one-third to two-thirds of any weight lost within a year-and all of it within five years. Doctors have wired patients' jaws closed, inflated plastic balloons inside their stomachs, performed massive excisions of body fat, prescribed amphetamines and large amounts of thyroid hormone, even performed neurosurgery to destroy the hunger centers in the brain's hypothalamus-and still people do not keep the weight off. Jaw wiring, for example, can produce substantial weight loss, and patients who ask for the procedure are highly motivated; yet some still take in enough liquid calories through their closed jaws to gain weight, and the others regain it once the wires are removed.We are a species that has evolved to survive starvation, not to resist abundance.

Children are the surprising exception to this history of failure. Nobody would argue that children have more self-control than adults; yet in four randomized studies of obese children between the ages of six and twelve, those who received simple behavioral teaching (weekly lessons for eight to twelve weeks, followed by monthly meetings for up to a year) ended up markedly less overweight ten years later than those who didn't; thirty per cent were no longer obese. Apparently, children's appetites are malleable. Those of adults are not.

There are at least two ways that humans can eat more than they ought to at a sitting. One is by eating slowly but steadily for far too long. This is what people with Prader-Willi syndrome do. Afflicted with a rare inherited dysfunction of the hypothalamus, they are incapable of experiencing satiety. And though they eat only half as quickly as most people, they do not stop. Unless their access to food is strictly controlled (some will eat garbage or pet food if they find nothing else), they become mortally obese.

The more common pattern, however, relies on rapid intake. Human beings are subject to what scientists call a "fat paradox." When food enters your stomach and duodenum (the upper portion of the small intestine), it triggers stretch receptors, protein receptors, and fat receptors that signal the hypothalamus to induce satiety. Nothing stimulates the reaction more quickly than fat. Even a small amount, once it reaches the duodenum, will cause a person to stop eating. Still we eat too much fat. How can this be? It turns out that foods can trigger receptors in the mouth which get the hypothalamus to accelerate our intake-and, again, the most potent stimulant is fat. A little bit on the tongue, and the receptors push us to eat fast, before the gut signals shut us down. The tastier the food, the faster we eat-a phenomenon called "the appetizer effect." (This is accomplished, in case you were wondering, not by chewing faster but by chewing less. French researchers have discovered that, in order to eat more and eat it faster, people shorten their "chewing time"-they take fewer "chews per standard food unit" before swallowing. In other words, we gulp.)

Apparently, how heavy one becomes is determined, in part, by how the hypothalamus and the brain stem adjudicate the conflicting signals from the mouth and the gut. Some people feel full quite early in a meal; others, like Vincent Caselli, experience the appetizer effect for much longer. In the past several years, much has been discovered about the mechanisms of this control. We now know, for instance, that hormones, like leptin and neuropeptide Y, rise and fall with fat levels and adjust the appetite accordingly. But our knowledge of these mechanisms is still crude at best.

Consider a 1998 report concerning two men, "BR" and "RH," who suffered from profound amnesia. Like the protagonist in the movie "Memento," they could carry on a coherent conversation with you, but, once they had been distracted, they recalled nothing from as recently as a minute before, not even that they were talking to you. (BR had had a bout of viral encephalitis; RH had had a severe seizure disorder for twenty years.) Paul Rozin, a professor of psychology at the University of Pennsylvania, thought of using them in an experiment that would explore the relationship between memory and eating. On three consecutive days, he and his team brought each subject his typical lunch (BR got meat loaf, barley soup, tomatoes, potatoes, beans, bread, butter, peaches, and tea; RH got veal parmigiana with pasta, string beans, juice, and apple crumb cake). Each day, BR ate all his lunch, and RH could not quite finish. Their plates were then taken away. Ten to thirty minutes later, the researchers would reappear with the same meal. "Here's lunch," they would announce. The men ate just as much as before. Another ten to thirty minutes later, the researchers again appeared with the same meal. "Here's lunch," they would say, and again the men would eat. On a couple of occasions, the researchers even offered RH a fourth lunch. Only then did he decline, saying that his "stomach was a little tight." Stomach stretch receptors weren't completely ineffectual. Yet, in the absence of a memory of having eaten, social context alone-someone walking in with lunch-was enough to re-create appetite.

You can imagine forces in the brain vying to make you feel hungry or full. You have mouth receptors, smell receptors, visions of tiramisu pushing one way and gut receptors another. You have leptins and neuropeptides saying you have either too much fat stored or too little. And you have your own social and personal sense of whether eating more is a good idea. If one mechanism is thrown out of whack, there's trouble.

Given the complexity of appetite and our imperfect understanding of it, we shouldn't be surprised that appetite-altering drugs have had only meagre success in making people eat less. (The drug combination of fenfluramine and phentermine, or "fen-phen," had the most success, but it was linked to heart-valve abnormalities and was withdrawn from the market.) University researchers and pharmaceutical companies are searching intensively for a drug that will effectively treat serious obesity. So far, no such drug exists. Nonetheless, one treatment has been found to be effective, and, oddly enough, it turns out to be an operation.

At my hospital, there is a recovery-room nurse who is forty-eight years old and just over five feet tall, with boyish sandy hair and an almost athletic physique. Over coffee one day at the hospital cafe, not long after my visit with Vincent Caselli, she revealed that she once weighed more than two hundred and fifty pounds. Carla (as I'll call her) explained that she had had gastric-bypass surgery some fifteen years ago.

She had been obese since she was five years old.She started going on diets and taking diet pills-laxatives, diuretics, amphetamines-in junior high school. "It was never a problem losing weight," she said. "It was a problem keeping it off." She remembers how upset she was when, on a trip with friends to Disneyland, she found that she couldn't fit through the entrance turnstile. At the age of thirty-three, she reached two hundred and sixty-five pounds. One day, accompanying her partner, a physician, to a New Orleans medical convention, she found that she was too short of breath to walk down Bourbon Street. For the first time, she said, "I became fearful for my life-not just the quality of it but the longevity of it."

This was 1985. Doctors were experimenting with radical obesity surgery, but there was dwindling enthusiasm for it. Two operations had held considerable promise. One, known as jejuno-ileal bypass-in which nearly all the small intestine was bypassed, so that only a minimum amount of food could be absorbed-was killing people. The other, stomach stapling, was proving not to be very effective over time; people tended to adapt to the tiny stomach, eating densely caloric foods more and more frequently.

Working in the hospital, however, Carla heard encouraging reports about the gastric-bypass operation-stomach stapling plus a rerouting of the intestine so that food bypassed only the duodenum. She knew that the data about its success was still sketchy, that other operations had failed, but in May of 1986, after a year of thinking about it, she had the surgery.

"For the first time in my life, I experienced fullness," she told me. Six months after the operation, she was down to a hundred and eighty-five pounds. Six months after that, she weighed a hundred and thirty pounds. She lost so much weight that she had to have surgery to remove the aprons of skin that hung from her belly and thighs down to her knees. She was unrecognizable to anyone who had known her before, and even to herself. "I went to bars to see if I could get picked up-and I did," she said. "I always said no," she quickly added, laughing. "But I did it anyway."

The changes weren't just physical, though. She said she felt a profound and unfamiliar sense of will power. She no longer had to eat anything: "Whenever I eat, somewhere in the course of that time I end up asking myself, 'Is this good for you? Are you going to put on weight if you eat too much of this?' And I can just stop." She knew, intellectually, that the surgery was why she no longer ate as much as she used to. Yet she felt as if she were choosing not to do it.

Studies report this to be a typical experience of a successful gastric-bypass patient. "I do get hungry, but I tend to think about it more," another woman who had had the operation told me, and she described an internal dialogue very much like Carla's: "I ask myself, 'Do I really need this?' I watch myself." For many, this feeling of control extends beyond eating. They become more confident, even assertive-sometimes to the point of conflict. Divorce rates, for example, have been found to increase significantly after the surgery. Indeed, a few months after her operation, Carla and her partner broke up.

Carla's dramatic weight loss has proved to be no aberration. Published case series now show that most patients undergoing gastric bypass lose at least two-thirds of their excess weight (generally more than a hundred pounds) within a year. They keep it off, too: ten-year follow-up studies find an average regain of only ten to twenty pounds. And the health benefits are striking: patients are less likely to have heart failure, asthma, or arthritis; eighty per cent of those with diabetes are completely cured of it.

I stopped in to see Vincent Caselli one morning in January of 2000, about four months after his operation. He didn't quite spring to the door, but he wasn't winded this time. The bags under his eyes had shrunk. His face was more defined. Although his midriff was vast, it seemed smaller, less of a sack.

He told me that he weighed three hundred and forty-eight pounds-still far too much for a man who was only five feet seven inches tall, but ninety pounds less than he weighed on the operating table. And it had already made a difference in his life. Back in October, he told me, he missed his youngest daughter's wedding because he couldn't manage the walking required to get to the church. But by December he had lost enough weight to resume going to his East Dedham garage every morning. "Yesterday, I unloaded three tires off the truck," he said. "For me to do that three months ago? There's no way." He had climbed the stairs of his house for the first time since 1997. "One day around Christmastime, I say to myself, 'Let me try this. I gotta try this.' I went very slow, one foot at a time." The second floor was nearly unrecognizable to him. The bathroom had been renovated since he last saw it, and Teresa had, naturally, taken over the bedroom, including the closets. He would move back up eventually, he said, though it might be a while. He still had to sleep sitting up in a recliner, but he was sleeping in four-hour stretches now-"Thank God," he said. His diabetes was gone. And although he was still unable to stand up longer than twenty minutes, his leg ulcers were gone, too. He lifted his pants legs to show me. I noticed that he was wearing regular Red Wing work boots-in the past, he had to cut slits along the sides of his shoes in order to fit into them.

"I've got to lose at least another hundred pounds," he said. He wanted to be able to work, pick up his grandchildren, buy clothes off the rack at Filenes, go places without having to ask himself, "Are there stairs? Will I fit in the seats? Will I run out of breath?" He was still eating like a bird. The previous day, he'd had nothing all morning, a morsel of chicken with some cooked carrots and a small roast potato for lunch, and for dinner one fried shrimp, one teriyaki chicken strip, and two forkfuls of chicken-and-vegetable lo mein from a Chinese restaurant. He was starting up the business again, and, he told me, he'd gone out for a business lunch one day recently. It was at a new restaurant in Hyde Park-"beautiful"-and he couldn't help ordering a giant burger and a plate of fries. Just two bites into the burger, though, he had to stop. "One of the fellas says to me, 'Is that all you're going to eat?' And I say, 'I can't eat any more.' 'Really?' I say, 'Yeah, I can't eat any more. That's the truth.' "

I noticed, however, that the way he spoke about eating was not the way Carla had spoken. He did not speak of stopping because he wanted to. He spoke of stopping because he had to. You want to eat more, he explained, but "you start to get that feeling in your insides that one more bite is going to push you over the top." Still, he often took that bite. Overcome by waves of nausea, pain, and bloating-the so-called dumping syndrome-he'd have to vomit. If there were a way to eat more, he would. This scared him, he admitted. "It's not right," he said.

Three months later, in April, Caselli invited me and my son to stop by his garage in East Dedham. My son was four years old and, as Vince remembered my once saying, fascinated with all things mechanical. The garage was huge, cavernous, with a two-story roll-up door and metal walls painted yellow. There, in the shadows, was Vince's beloved Gradall, a handsome tank of a machine, as wide as a county road, painted yield-sign yellow, with shiny black tires that came up to my chest and his company name emblazoned in curlicue script along its flanks. On the chassis, six feet off the ground, was a glass-enclosed control cab and a thirty-foot telescoping boom, mounted on a three-hundred-and-sixty-degree swivel. Vince and a friend of his, a fellow heavy-equipment contractor I'll call Danny, were sitting on metal folding chairs in a sliver of sunlight, puffing fat Honduran cigars, silently enjoying the day. They both rose to greet us. Vince introduced me as "one of the doctors who did my stomach operation."

I let my son go off to explore the equipment and asked Vince how his business was going. Not well, he said. Except for a few jobs in late winter plowing snow for the city in his pickup truck, he had brought in no income since the previous August. He'd had to sell two of his three pickup trucks, his Mack dump truck, and most of the small equipment for road building. Danny came to his defense. "Well, he's been out of action," he said. "And you see we're just coming into the summer season. It's a seasonal business." But we all knew that wasn't the issue.

Vince told me that he weighed about three hundred and twenty pounds. This was about thirty pounds less than when I had last seen him, and he was proud of that. "He don't eat," Danny said. "He eats half of what I eat." But Vince was still unable to climb up into the Gradall and operate it. And he was beginning to wonder whether that would ever change. The rate of weight loss was slowing down, and he noticed that he was able to eat more. Before, he could eat only a couple of bites of a burger, but now he could sometimes eat half of one. And he still found himself eating more than he could handle. "Last week, Danny and this other fellow, we had to do some business," he said. "We had Chinese food. Lots of days, I don't eat the right stuff-I try to do what I can do, but I ate a little bit too much. I had to bring Danny back to Boston College, and before I left the parking lot there I just couldn't take it anymore. I had to vomit.

"I'm finding that I'm getting back into that pattern where I've always got to eat," he went on. His gut still stopped him, but he was worried. What if one day it didn't? He had heard about people whose staples gave way, returning their stomach to its original size, or who managed to put the weight back on in some other way.

I tried to reassure him. I told him what I knew Dr. Randall had already told him during a recent appointment: that a small increase in the capacity of his stomach pouch was to be expected, and that what he was experiencing seemed normal. But could something worse happen? I didn't want to say.

Among the gastric-bypass patients I had talked with was a man whose story remains a warning and a mystery to me. He was forty-two years old, married, and had two daughters, both of whom were single mothers with babies and still lived at home, and he had been the senior computer-systems manager for a large local company. At the age of thirty-eight, he had had to retire and go on disability because his weight-which had been above three hundred pounds since high school-had increased to more than four hundred and fifty pounds and was causing unmanageable back pain. He was soon confined to his home. He could not walk half a block. He could stand for only brief periods. He went out, on average, once a week, usually for medical appointments. In December, 1998, he had a gastric bypass. By June of the following year, he had lost a hundred pounds.

Then, as he put it, "I started eating again." Pizzas. Boxes of sugar cookies. Packages of doughnuts. He found it hard to say how, exactly. His stomach was still tiny and admitted only a small amount of food at a time, and he experienced the severe nausea and pain that gastric-bypass patients get whenever they eat sweet or rich things. Yet his drive was stronger than ever. "I'd eat right through pain-even to the point of throwing up," he told me. "If I threw up, it was just room for more. I would eat straight through the day." He did not pass a waking hour without eating something. "I'd just shut the bedroom door. The kids would be screaming. The babes would be crying. My wife would be at work. And I would be eating." His weight returned to four hundred and fifty pounds, and then more. The surgery had failed. And his life had been shrunk to the needs of pure appetite.

He is among the five to twenty per cent of patients-the published reports conflict on the exact number-who regain weight despite gastric-bypass surgery. (When we spoke, he had recently submitted to another, more radical gastric bypass, in the desperate hope that something would work.) In these failures, one begins to grasp the power that one is up against. An operation that makes overeating both extremely difficult and extremely unpleasant-which, for more than eighty per cent of patients, is finally sufficient to cause appetite to surrender and be transformed-can sometimes be defeated after all. Studies have yet to uncover a single consistent risk factor for this outcome. It could, apparently, happen to anyone.

It was a long time before I saw Vince Caselli again. Earlier this year, I called him to ask about getting together, and he suggested that we go out to see a Boston Bruins game. A few days later, he picked me up at the hospital in his rumbling Dodge Ram. For the first time, he looked almost small in the outsized truck. He was down to about two hundred and fifty pounds. "I'm still no Gregory Peck," he said, but he was now one of the crowd-chubby, in an ordinary way. The rolls beneath his chin were gone. His face had a shape. His middle no longer rested between his legs. And, almost a year and a half after the surgery, he was still losing weight. At the FleetCenter, where the Bruins play, he walked up the escalator without getting winded. Our tickets were taken at the gate-the Bruins were playing the Pittsburgh Penguins-and we walked through the turnstiles. Suddenly, he stopped and said, "Look at that. I went right through, no problem. I never would have made it through there before." It was the first time he'd gone to an event like this in years.

We took our seats about two dozen rows up from the ice, and he laughed a little about how easily he fit. The seats were as tight as coach class, but he was quite comfortable. (I, with my long legs, was the one who had trouble finding room.) Vince was right at home here. He had been a hockey fan his whole life, and could supply me with all the details: the Penguins' goalie Garth Snow was a local boy from Wrentham and a friend of one of Vince's cousins; Joe Thornton and Jason Allison were the Bruins' best forwards, but neither could hold a candle to the Penguins' Mario Lemieux. There were nearly twenty thousand people at the game, but within ten minutes Vince had found a friend from his barbershop sitting just a few rows away.

The Bruins won, and we left cheered and buzzing. Afterward, we went out to dinner at a grill near the hospital. Vince told me that his business was finally up and running. He could operate the Gradall without difficulty, and he'd had full-time Gradall work for the past three months. He was even thinking of buying a new model. At home, he had moved back upstairs. He and Teresa had taken a vacation in the Adirondacks; they were going out evenings, and visiting their grandchildren.

I asked him what had changed since I saw him the previous spring. He could not say precisely, but he gave me an example. "I used to love Italian cookies, and I still do," he said. A year ago, he would have eaten to the point of nausea. "But now they're, I don't know, they're too sweet. I eat one now, and after one or two bites I just don't want it." It was the same with pasta, which had always been a problem for him. "Now I can have a bite and I'm satisfied."

Partly, it appeared that his taste in food had changed. He pointed to the nachos and buffalo wings and hamburgers on the menu, and said that, to his surprise, he no longer felt like eating any of them. "It seems like I lean toward protein and vegetables nowadays," he said, and he ordered a chicken Caesar salad. But he also no longer felt the need to stuff himself. "I used to be real reluctant to push food away," he told me. "Now it's just-it's different." But when did this happen? And how? He shook his head. "I wish I could pinpoint it for you," he said. He paused to consider. "As a human, you adjust to conditions. You don't think you are. But you are."

These days, it isn't the failure of obesity surgery that is prompting concerns but its success. Physicians have gone from scorning it to encouraging, sometimes imploring, their most severely overweight patients to undergo a gastric-bypass operation. That's not a small group. More than five million adult Americans meet the strict definition of morbid obesity. (Their "body mass index"-that is, their weight in kilograms divided by the square of their height in metres-is forty or more, which for an average man is roughly a hundred pounds or more overweight.) Ten million more weigh just under the mark but may nevertheless have obesity-related health problems that are serious enough to warrant the surgery. There are ten times as many candidates for obesity surgery right now as there are for heart-bypass surgery in a year. So many patients are seeking the procedure that established surgeons cannot keep up. The American Society of Bariatric Surgery has only five hundred members nationwide who perform gastric-bypass operations, and their waiting lists are typically months long. Hence the too familiar troubles associated with new and lucrative surgical techniques (the fee can be as much as twenty thousand dollars): newcomers are stampeding to the field, including many who have proper training but have not yet mastered the procedure, and others who have no training at all. Complicating matters further, individual surgeons are promoting a slew of variations on the standard operation which haven't been fully researched-the "duodenal switch," the "long limb" bypass, the laparoscopic bypass. And a few surgeons are pursuing new populations, such as adolescents and people who are only moderately obese.

Perhaps what's most unsettling about the soaring popularity of gastric-bypass surgery, however, is simply the world that surrounds it. Ours is a culture in which fatness is seen as tantamount to failure, and get-thin-quick promises-whatever the risks-can have an irresistible allure. Doctors may recommend the operation out of concern for their patients' health, but the stigma of obesity is clearly what drives many patients to the operating room. "How can you let yourself look like that?" is society's sneering, unspoken question, and often its spoken one as well. Women suffer even more than men from the social sanction, and it's no accident that seven times as many women as men have had the operation. (Women are only an eighth more likely to be obese.)

Indeed, deciding not to undergo the surgery, if you qualify, is at risk of being considered the unreasonable thing to do. A three-hundred-and-fifty-pound woman who did not want the operation told me of doctors browbeating her for her choice. And I have learned of at least one patient with heart disease being refused treatment by a doctor unless she had a gastric bypass. If you don't have the surgery, you will die, some doctors tell their patients. But we actually do not know this. Despite the striking improvements in weight and health, studies have not yet proved a corresponding reduction in mortality.

There are legitimate grounds for being wary of the procedure.As Paul Ernsberger, an obesity researcher at Case Western Reserve University, pointed out to me, many patients undergoing gastric bypass are in their twenties and thirties. "But is this really going to be effective and worthwhile over a forty-year span?" he asked. "No one can say." He was concerned about the possible long-term effects of nutritional deficiencies (for which patients are instructed to take a daily multivitamin). And he was concerned about evidence from rats that raises the possibility of an increased risk of bowel cancer.

We want progress in medicine to be clear and unequivocal, but of course it rarely is. Every new treatment has gaping unknowns-for both patients and society-and it can be hard to decide what to do about them. Perhaps a simpler, less radical operation will prove effective for obesity. Perhaps the long-sought satiety pill will be found. Nevertheless, the gastric bypass is the one thing we have now that works. Not all the questions have been answered, but there are more than a decade of studies behind it. And so we forge ahead. Hospitals everywhere are constructing obesity-surgery centers, ordering reinforced operating tables, training surgeons and staff. At the same time, everyone expects that, one day, something new and better will be discovered that will make what we're now doing obsolete.

Across from me, in our booth at the grill, Vince Caselli pushed his chicken Caesar salad aside only half eaten. "No taste for it," he said, and he told me he was grateful for that. The operation, he said, had given him his life back. But, after one more round of drinks, it was clear that he still felt uneasy.

"I had a serious problem and I had to take serious measures," he said. "I think I had the best technology that is available at this point. But I do get concerned: Is this going to last my whole life? Someday, am I going to be right back to square one-or worse?" He fell silent for a moment, gazing into his glass. "Well, that's the cards that God gave me. I can't worry about stuff I can't control."