Stacy London, co-host of TLC’s fashion makeover show “What Not To Wear,” was recently stopped at her local Met supermarket in Brooklyn’s Carroll Gardens by a large, imposing-looking man. “You’re from that TV show,” he said. I told my wife you lived in this neighborhood, but she didn’t believe me. She loves your show. If you ever need anything,” he said, with a knowing look, “You come find me.” It was official: Ms. London had become a celebrity.

Two weeks ago, when Ms. London arrived at Olives restaurant on Park Avenue South for an interview and photo shoot, there was no question of her celebrity status. Two stylists – one for hair and one for makeup – were on hand, along with two publicists representing Bali, a lingerie company whose latest line Ms. London is promoting. Passersby peered in the windows for a glimpse of the proceedings. Ms. London, who is 35, cheerfully bemoaned the fact that she had spent the predawn hours doing interviews by satellite with TV stations around the country to discuss Bali’s new bra line. “I’ve been up since 3 a.m. Try to make me look good,” she pleaded jokingly with the photographer.

Making others look good is, in fact, the focus of Ms. London’s career. Last week, she began taping the third season of “What Not To Wear,” in which she and her co-host, Clinton Kelly, make over an individual (usually a woman) who has been nominated by her friends for having terrible fashion taste. The makeover candidate is secretly videotaped for a few days, displaying a range of bad clothing choices, then is ambushed by Ms. London and Mr. Kelly, who “kidnap” the victim to New York City, go through her wardrobe, disposing of many garments, and offer a set of fashion rules for her to follow when shopping. The makeover subject is then given a budget of $5,000 and sent to clothing stores to acquire an improved wardrobe, applying the fashion principles she has learned from the duo.

Adapted from a British TV series of the same name, the show is fairly addictive, in part because of the wisecracking banter between Ms. London and Mr. Kelly, who maintain a relationship that Mr. Kelly has compared to that of “a brother and sister on a very long car ride.”

Fashion wasn’t an obvious career choice for Ms. London. Growing up in New York City, Ms. London attended Trinity High School on the Upper West Side and split her time between the homes of her father, Herb London, an NYU professor, the former dean of NYU’s Gallatin School of Individualized Study and the president of the Hudson Institute, and her mother, Joy London, who worked as a venture capitalist before retiring. She went on to Vassar College, where she majored in German philosophy and literature, and initially assumed she would write or teach in one of those fields after college. She became increasingly interested in the idea of writing for a magazine, however, and found herself particularly drawn to the gorgeous images and spreads of fashion magazines. A connection through a friend helped her land a summer internship with the public relations department of Christian Dior in Paris, where she had her first real exposure to fashion. “I was dazzled. I’d never seen anything more magnificent in my life,” she recalled.

After college, she was hired by Vogue magazine, where she “really got a fashion education.” After two years at Vogue, she left to freelance, working as a guest editor and stylist at a number of magazines. At age 26, she got her big break – a job as a senior fashion editor at Mademoiselle. After four years there, in 2000, she struck out on her own again, working as a stylist for a roster of private clients that ranged from celebrities (she won’t name names) to high-level businesswomen who needed fashion guidance.

Then she got a call from the producers of “What Not To Wear.” This wasn’t her first experience with television – she had done work with MTV and VH1 while still at Mademoiselle – but she went through “four nerve-wracking screen tests” before landing the part. Her co-host for the show’s first season was a long-haired stylist named Wayne Scot Lukas; he was replaced in the second season by Mr. Kelly, formerly the executive editor at DNR, a news magazine devoted to men’s fashion. Ms. London says she’s had great chemistry with both co-hosts.

The show really took off in its second season, however. “I’m very proud of the second season,” Ms. London said, noting that in the first season the show had 10 episodes; in the second, it grew to 50.

In addition to the show’s fashion component, Ms. London loves the psychological aspects of the show. “Every different type of interpersonal relationship is played out at some point in reality TV,” she said. She feels that the style makeovers that the show’s subjects receive give them greater self-esteem and self-confidence in other areas of their lives. “After the show, people have left jobs they hated and found new careers. They’ve left bad relationships,” she said. She has kept in touch with many of the people she’s made over on the show, many of whom still e-mail her for fashion advice on occasion.

Ms. London is excited about the show’s third season, which will include specials such as a crossover double episode with the TLC home-improvement show “While You Were Out”; a makeover of the “worst-dressed couple in America,” and an episode where the usual $5,000 clothing budget is increased to $50,000. And for those who wish to nominate themselves for an off-camera makeover, Bali is hosting a contest at www.balicompany.com for the chance to win a makeover by Ms. London and $5,000 for a new wardrobe.

Ms. London’s biggest upcoming project, however, may be the planning of her own wedding to fiance Mark Riebling, a writer and the editorial director of the Manhattan Institute for Policy Research, to whom she’s been engaged for a year and two months. Ms. London, who is always decisive and opinionated about fashion on “What Not to Wear,” remains undecided about the look of her wedding. “When I was little, my dream was always to get married at the St. Regis. I wanted old, old-school New York. And now I’m torn between that and doing something really funky and modern,” she said. “I went through a phase where I thought, ‘I’m not going to wear white, I’m going to wear a green silk cocktail dress. I’m going to be different,'” she added. “Now I’m so attracted to all these incredibly traditional bridal gowns. If I wind up in one of those, shoot me.”

As for the upcoming fashion season, Ms. London said that body-conscious cuts will be popular: One of the reasons she decided to work with Bali on its new line is that she wants to impress upon women that finding the right bra is essential for pulling off form-fitting looks. She also predicted that texture will be a key fashion element, from tweed and Fair Isle patterns to sequin and beading embellishments.

Ms. London seemed to embody this style already: She wore a Nanette Lepore cream chiffon-silk blouse adorned with black sequins and beads, a cropped pinstriped jacket with rhinestone-embellished buttons (“I have no idea who it’s by,” she said), and knee-high boots by Isaac Mizrahi. Ms. London knows, however, that the best looks don’t necessarily come from high-priced brands or trendy designers: The jeans she wore were from the Gap.