Gloria Cahill lost 140 pounds.   (Photo: Danielle Levitt)

In some ways, answering this question is just the beginning. Dramatic weight loss has a way of exposing not just the architecture of people’s bodies but of their lives—the subtle economies of power in their relationships, the suitability of their work, the limits of their own strength—and that architecture may not look nearly as lovely. A woman may discover that her marriage of twenty years was predicated on a dynamic of disrespect and condescension, or that her best friend since childhood required a sidekick who didn’t threaten her somehow. Then again, she may also discover that the man she’s been married to is made of even kinder, sturdier stuff than she ever imagined, and that her friends have a capacity for generosity more profound than she’s ever known. It simply depends. Results, as they say in diet commercials, may vary.

“There was a night—this was maybe a year and a half ago—when a really gorgeous twentysomething Frenchman spent the bulk of a party sitting on the coffee table in front of me, just listening. That was fun.”

This is Gloria Cahill, 46, director of NYU’s Office of Community Service. She had gastric-bypass surgery four years ago.

“We were in a room full of people, and a lot of them were the kind of girl-woman who used to be the bane of my high-school existence—beautiful, self-confident, not above the occasional fat joke,” she continues. “They were all looking on, wanting to know who he was and, probably more to the point, who the hell I was. That was satisfying. At the end of the evening, all I could think was, ‘This is a new approach to parties.’ I went from being a wallflower to . . . I don’t know. A bouquet.”

Warm, sensitive, and brimming with opinions, Cahill has a lively knack for describing the effects of her operation. She’s actually 200 pages into writing a book about it, part of a collaborative effort with her surgeon, Mitchell Roslin, who helped operate on Al Roker at Lenox Hill. In one chapter, she likens her new body to a cereal box whose contents have settled.

“She lost a whole person, and became someone different.”

“Oh, and then—” she remembers. “This was maybe two years ago. At a local benefit. I was wearing high heels and a slinky black dress with a slit up the side. And a very attractive man parked himself at my table, smiled a bit mischievously, and declared, ‘I’m very partial to redheads.’ ”

In the history of pickup lines, that one probably wasn’t the most deft, I admit. But it wasn’t the worst—

“Yes, but it wasn’t my hair he was looking at,” she says, then bursts out laughing. “He said it two or three times, as if it were meant to be charming. I had never experienced that kind of misguided flattery. It was the construction worker’s wolf whistle in stockbroker’s clothing.”

Until her surgery, Cahill had spent almost her entire life as a fat girl—shopping at the “Chubby Shop” section of Lane Bryant, attending her first Lean-Line meetings in eighth grade. She finally decided to have her operation after her mother, also morbidly obese, died in 2000. At the time, Cahill was 275 pounds, and her sister, roughly the same weight and ten years her senior, was already struggling with horribly debilitating medical problems. Cahill was terrified she was staring into a crystal ball.

Today, Cahill is 135 pounds. She blazes up stairwells; hikes up mountains; twists herself into yoga poses, luxuriating in the sensuality of her corkscrew limbs. Adjusting to her new contours took time—a few months after the surgery, Cahill said “excuse me” to her own reflection before running into a mirror—but she also had a premonition: “Before I lost the weight, I had this sneaking suspicion I bore a resemblance to Annette Bening,” she says. “I never, ever, would have said it out loud—I’d have been laughed out of the room—but since I lost the weight, so many people have said it.”

Under the circumstances, you’d think Cahill would be catnip to men. But her social life is more complicated than that. Like many people who’ve been heavy, Cahill missed some of the crucial rites that demystify the dating process. (Doctors often talk about this phenomenon: “They’ve never gone through that teenage thing of holding hands,” says Alfons Pomp, a surgeon at New York-Presbyterian Hospital/Weill Cornell, “so they meet someone in a bar and wind up in Europe for the weekend.”)