Gustatory marathon man Adam Sachs shadows Lance Armstrong—eating up the French countryside for real

There are crumbs on the dashboard. Two bikes are clanging from side to side in the rear of the speeding hatchback as we take the swervy curves of the two-lane D952 northeast from Aix into the hills of Haute Provence.

The driver (my friend Dennis) continues to accelerate while thoughtfully eating a cookie. In place of a map, the navigator (me) clutches a wine-stained, lustily underlined paperback copy of Waverley Root's The Food of France. A sweaty, athletic kind of silence prevails in the hatchback. We are "in the zone." Which is to say we are: still digesting the Michelin-two-star dinner of the night before that concluded with very old Armagnac; hung over; eating cookies for breakfast and doggedly focusing on the race to our next meal. It's early on day eight of our sweeping, self-imposed, hard-driving, light-biking, all-consuming culinary Tour de France, and we are already late for lunch.

Ah, lunch…

But first, about that book. Waverley Root was an American newspaperman in Paris from the 1920s through the postwar years. He split his time between his day job, filing stories for the Chicago Tribune and other papers, and his calling: developing an astonishingly comprehensive guide to the gastro-anthropological minutiae that is regional French cooking. He embodied the belief of his friend and fellow trencherman A. J. Liebling that "the primary requisite for writing well about food is a good appetite."

Published in 1958, The Food of France isn't a guide in the normal sense. Its maps lack topographic detail. Instead, they are annotated with the names of the edible specialties of the area. For instance, the suburbs of Grenoble are labeled ST. MARCELLIN CHEESE, WALNUTS, AND GRATIN DAUPHINOIS, while the nearby city of Vienne is marked FOIE GRAS IN PASTRY and TROUT BRAISED IN PORT. As if these were physical facts of the landscape. As if you could jump in your car and head north on the autoroute from Grenoble, watching a giant gratin recede in the rearview mirror as the rich goose liver pastry and trout of Vienne come into view on the fragrant horizon.

Fifty years on, Root's book is still as clear as consommé and as complex and satisfying as quality cassoulet. The first time I read it, I went through it cover to cover like a novel. Good reading though it is, I've always wanted to do more with it—specifically, to eat my way through its index. So when the editors of Condé Nast Traveler called me to discuss a culinary odyssey in the spirit of the Tour de France, I immediately envisioned Root's division of French cooking into three territories, each named for its signature cooking fat: the Domain of Lard, the Domain of Oil, and the Domain of Butter.

A plan emerged. To eat my way through as much of France as possible over two weeks, tracing.. roughly the path taken by riders on the Tour, which itself swallows up every conceivable type of terrain in its two-thousand-mile circumnavigation of the country. To do it during the race itself, the showiest time of year for every village, town, and city in the Tour's path. To bike parts of the route myself (this, at least, in moderation). And to run a kind of marathon of my own—part road rally, part gustatory endurance test. Looking for a teammate, I called my old friend Dennis Leary in San Francisco. Dennis had just left his job as the top chef at the highly regarded Rubicon and was going to open his own place in a few weeks. Besides a Rootian knowledge of Mediterranean food, Dennis had the added qualification of having twice cooked dinner for Lance Armstrong. The race was on.