In high school, "Mike" was in the closet. He couldn't talk to anyone about how he got aroused by fat women. "I'd like a girl and worry that she wouldn't be into it," says the 23-year-old environmental-science student and self-proclaimed feeder in northern New Jersey. "But once I got online, I found out that this thing had a name." (Some in the scene refer to their "feeder-dar": "A lot of girls who like large men are in the closet," Rivera says. "It's like the new gay.")

Mike dated average-size women, even thin women, but he couldn't get fat chicks out of his head. Last year, he joined a Yahoo Group called JackisJellyBelly. "Jacki" was a 33-year-old, five-foot-four woman who spent a year growing herself from 150 pounds to 226. Mike was attracted to her confidence—and her fleshy curves. "She was like the skinny girl who stops working out and becomes a BBW," Mike says. "I went gaga over her body."

After an instant-message courtship, Mike drove to Pennsylvania and took Jacki to a Chinese buffet and a movie. Their age difference concerned them at first, but they shared enough interests—especially feeding. Together, they lived out their fantasies. Jacki's weight had dipped to 210 after a nasty cough, but Mike quickly remedied that with carloads of cannolis, cream puffs, and eclairs from his local bakery. Once, he brought her a tiramisu cake; she consumed it over two days, on top of her customary 3,000 calories. Mike would feed her jumbo pastries while she lounged in a T-shirt and panties. When they finished their foreplay—"just desserts," they called it—they would tear off each other's clothes for feverish sex. In five months, she gained 16 pounds.

But even during sex, Mike says, he fantasizes about having a partner who's even larger. Over the years, he's amassed thousands of images of fat women. He's even attracted Internet fans with his homemade porn, in which Jacki ate Breyer's vanilla ice cream while he rubbed lotion on her belly.

"I could feed her and get aroused," Mike says. "It would happen every day: not just once a day, but over and over. I get off on the gluttony—to me, it's the hottest thing. It works better than Viagra."

That's the biggest difference between the amateurs, who break out cans of novelty-shop whipped cream to spice up their sex life, and the serious feeders, whose eating eclipses every other activity—including sex, which becomes less and less frequent as one or both partners pass the 400-pound mark, making traditional sex positions impractical. The obese body becomes a symbol for both feeder and gainer, Kulick notes in Fat, and each accrued pound becomes a reminder of a hot night of bingeing.

Most feeders (or feedees) say they want to stuff (or be stuffed) in the context of a normal, loving relationship. Mike speaks wistfully about Jacki, whom he's taking a break from dating, and muses on how hard it is to meet a woman he really likes who also loves to eat—and eat, and eat—in bed. Yet it's easy to see how neatly each role fits into one side of the S&M ampersand. And how, in fat-phobic America, where obesity seems a fate worse than death, such an arrangement might seem abusive, even suicidal.