Can America's most health-conscious city have world-class restaurants? A skeptic investigates.

All this healthy's hurting my head. I've just driven into downtown Boulder, Colorado, after flying in from New York City, and already I've spotted five mountain bikers, two in-line skaters and countless joggers, all frolicking in the sun. Locals, most of whom appear to be tan and fit, are fond of pointing out that their city has more days of sunshine than San Diego.

Boulder's Alpine blue skies and gorgeous Rocky Mountain setting have made it a kind of sports heaven. Boulder was recently voted "Number One Running City" by Runner's World, "Best Place to Be an Überjock" by Outside and "Thinnest City in America" by Self. As promised, Boulderites are an active bunch; you get the feeling that anyone who joins the city's tax rolls is immediately given an SUV with a ski-and-bike rack and a full wardrobe of Patagonia fleece.

Despite Boulder's obsession with fitness, some excellent restaurants had recently opened here, I'd heard, one co-owned by two alums of Napa Valley's vaunted French Laundry. I'm skeptical about finding great food in a town like this, but curious enough to pay a visit.

My outlook doesn't improve when I reach the five-month-old Frasca Food and Wine and find chef Lachlan MacKinnon-Patterson outside, rhapsodizing about a shipment of lettuce. His supplier, a ponytailed guy in flannel, is showing off a carton of roughage. "We call one of our salads Hearts and Souls because it gets to the very center, the essence of each lettuce," MacKinnon-Patterson explains to me, holding up a red-veined specimen. The ponytailed guy listens intently. "That's beautiful, man," he says. MacKinnon-Patterson, 29, and his partner, Master Sommelier Bobby Stuckey, 35—both veterans of the French Laundry—modeled Frasca on the canteens of Italy's Friuli region. While touring the U.S. to look for a location, they visited Boulder's famous farmers' market, which runs from spring until mid-fall. "We just freaked out," Stuckey says, referring to the outstanding produce going largely unused by local restaurants. "Boulder today is like Berkeley was 25 years ago," MacKinnon-Patterson adds.

I'm starting to panic about the prospect of a dinner based around lettuce, but a glass of Movia Ribolla, a medium-bodied Slovenian white wine from Stuckey's 250-bottle list, takes the edge off. And to my surprise, the Hearts and Souls salad—made from lettuce hearts and dressed in a pickled-shallot vinaigrette—genuinely sparkles. But what comes next really sells me on Frasca: tender lamb loin from a nearby farm, crusted with mint-brioche bread crumbs, and ultrasoft gnocchi in bloodred beet sauce.

Just down Pearl Street, Boulder's main drag, is six-month-old Blue Fine Pastries. I stop in and chat with the 34-year-old co-owner and pastry chef, Jen Bush. This is clearly no joyless vegan outpost. Bush creates seriously rich desserts: mocha pyramids filled with hazelnut crème and dusted with gold leaf; ready-to-bake cookie-dough rolls in flavors like Snickerdoodle; and seasonal muffins. It occurs to me that all that exercise may be just an excuse for Boulderites to eat anything they want.

The next night, I visit nine-month-old The Kitchen, whose English-born co-chef and co-owner, Hugo Matheson, is a former colleague of Jamie Oliver's at London's River Cafe. Matheson, 36, is appropriately skeptical of all things American—including Boulder's fitness culture: "You walk down the street and everybody's got their gear on. I mean, 200-pound men in Spandex. That's scary." But he does share the city's eco-conscious sensibility: The Kitchen buys power generated by wind turbines, and Matheson gives his used cooking oil to a guy who converts it into bio-diesel fuel. (Matheson says that when you drive behind the man's truck, you can smell french fries.) He also can't hide his passion for the local ingredients; on the restaurant's walls are blackboards listing the purveyors who sell him the foods he builds his dishes around. The mountains are part of his inspiration. "You're here in all this beauty, and you want a little cheese or pâté or something," he says. "What are you going to do? Go to the gas station for a Twinkie?"

Matheson keeps his food simple: a poached duck egg from the upstairs-neighbor's farm, served on truffled pasta; fresh chanterelles on toast; steak frites, a dish that's not often on the menu but that regulars know to ask for. The flavors are precise and powerful. This isn't food that puts you in mind of rigorous exercise, but after dinner, talk turns that way. "I think it's a law that you have to own a mountain bike here," Matheson says, gloomily. "Whatever happened to a good walk?"

I agree. (On second thought, skip the walk. I'll take a cab.) But to get a grasp on local culture, I sign up for a rock-climbing session with Ashley Woods, co-owner of the Spot Bouldering Gym. "There's so much to do every weekend that it's hard to decide," she says cheerily as we drive the 15 minutes to Boulder Canyon. "Do I want to ski? Do I want to ice climb? Rock climb? Go biking?" What about sitting on the couch, drinking a Bloody Mary, watching TV?

Moments later, Woods parks the car, points to a 40-foot-high slab of rock and suggests the impossible: that I climb this obviously unclimbable wall. Harnessed, helmeted and wearing sticky climbing shoes, I start upward gingerly, panting in the thin air. The first steps are easy but then each becomes a puzzle. Near the top, I get stuck; there's no place to put my foot. Clinging to the wall with my fingertips, I prod a bump with my toe. "Yes," Woods yells. "Trust the foot!" Miraculously, the foot holds.

"That glass of wine will feel good tonight," Woods says when I'm on firm ground. Exhilarated and exhausted, I know she's right. And for the first time, I can see the virtue of pushing my body before rewarding it—but I don't plan on making a habit of it.

Brett Martin is a freelance writer living in Brooklyn, New York. He has written for Vanity Fair and GQ.