Can you wine and dine in France for two weeks without gaining an ounce? Susan Squire takes a hike to find out

The experiment gets rolling at 10 a.m. when we step on our respective scales, Rebecca in D.C. and me in New York. It will conclude with a second weigh-in seventeen days hence. The numerical comparison between now and then (higher, lower, same) will tell the tale.

The question: Can two women—sisters, actually, eighteen months and one pound apart as of this morning—spend a fortnight traveling through France, eating and drinking with impunity, and not gain an ounce? Our strategy is simple: We'll match intense caloric consumption with intense caloric expenditure, the latter of the low-tech, readily available variety known as walking. Ten to fifteen miles a day, from one hotel to the next, with our stuff on our backs. But don't call it backpacking; call it adventure travel for sybaritic Luddites. We'll be sleeping in good hotels, not in tents, and if time gets tight, we'll allow ourselves the occasional train or taxi.

We're headed for the underexplored region of Franche-Comté—south of Alsace, east of Burgundy, on the Swiss border—where the footpaths are supposedly among the most thrilling of France's 25,000-mile national network. The area lacks the glitz of the Côte d'Azur and the snob appeal of Provence, but it has plenty of seductive inns and good restaurants. The landscape is diverse enough to prevent walker's ennui—and fruitful enough to supply the ingredients of a distinctive cuisine. There are forests carpeted in wild mushrooms, multitudinous rivers teeming with trout, and lush grasslands to nurture the cows whose milk yields the region's signature cheeses: Comte, Morbier, bleu de Gex, and the celestial vacherin. Perfect, in other words, for us.

After landing at Charles de Gaulle at about half-past six, we're in transit for seven hours on various high- and low-speed trains. At Mouchard, we transfer to a bus bound for the town of Arbois, in the Jura, a département of Franche-Comté that is famed for its mountains and vineyards. Arbois is billed by Franche-Comté's tourist office as the region's 'wine capital'; more to the point, it's where chef Jean-Paul Jeunet reputedly works wonders in the kitchen of his eponymous Michelin-starred restaurant. Since the establishment also offers lodging, we'll eat and sleep there tonight.

The driver dumps us unceremoniously at the side of a narrow road that turns out to be Arbois's main drag. Crepe paper bunches of purple and green grapes are strung overhead in honor of tomorrow's wine festival. While the village's cuteness quotient is high, our moods are not: We've discovered that our fully loaded not-really-backpacks are too heavy to carry for five minutes, let alone fifteen miles. Under a blazing sun, we literally kick them up a narrow sidewalk until we find the Jeunet establishment—just as a sudden monsoon erupts from out of nowhere.

A chilly blond checks us into a clean, quiet room with tall windows: a steal at seventy-five dollars. Ditching the loathsome luggage, we repair to a nearby wine bar for lunch. It's nearly four when we finish, ludicrously late to start a hike, but it's stopped raining and we must work off the smoked trout and cheesy onion soup before dark. The map shows a footpath running from the center of town to a prehistoric grotte (cave). The round-trip is a measly eight miles, still better than nothing. Yawning from food, wine, and jet lag, we leave the restaurant and spend the next half-hour trying to find the footpath promised on the map. Instead we end up on a paved road, which is fortunately devoid of traffic. and I are the only ambulatory objects around, save for grazing cows and the flies that love them.