This week, his 13th on the road, has been the hardest thus far for Steve Vaught, a 400-pound man trying to walk across America.

On Sunday morning, he found a creek just as the desert heat forced a midday break. But when he woke from a nap and tried to fill his water bottles, the stream had already gone dry. Late that night, he walked right past his scheduled motel stop in Truxton, a flyspeck on historic Route 66 so slight it vanished when the sun went down.

On Monday, out of water in 102-degree heat and miles from any town, he sent a frantic text message to his wife, who called the local police. They drove him to a hotel, where he rested a night and a day, sick with dehydration. On Wednesday he started late and tangled with a scary dude on the desolate highway.

"I'm quitting," he told his wife this week. She said okay.

But within hours he hit the road again, as they always sort of knew he would. For quitting is not so easy when you're 500 miles from home.

This spring, as he neared his 40th birthday, Vaught had an epiphany: If he didn't lose the weight, he would die before 50. But dieting would not work, he decided, and neither would normal exercise. He knew he was the kind of guy who could rationalize his way out of one three-mile walk after another. "My weakness," he said, "is the easy way out."

So Vaught made it hard. On April 10, he left his home in San Diego -- and his wife and two children -- and started walking, alone, to New York.

There's something about this nation's geography that inspires this kind of journey -- to hike the Appalachian Trail, to kayak the entire Mississippi River, or just to drive from Maine to Key West, and maybe make sense of things along the way. Which is how it has gone for Vaught, on the road mulling issues far beyond weight or willpower. The trip has not gone completely as planned. He has only rarely come even close to the pace of 20 miles a day he estimated would put him in verdant Missouri by now, not Arizona in July.

He strained a couple of ligaments shortly after he started, and he lost three toenails climbing the final mountain pass out of California.

If he is very lucky, Vaught will clear 80 miles this week, a fraction of his 3,000-mile goal. On Wednesday, he remained deeply concerned about his ability to cover a 25-mile stretch of uninhabited desert between Seligman and Ash Fork.

On the bright side: That 400-pound man now weighs only 350.

Health Implications

"Does this seem insane?" Vaught wants to know.

He is a big guy, 6-foot-1, a former Marine and longtime tow-truck operator who, as the fat melts away from his cheekbones and jaws, is beginning to bear a slight resemblance to the buffed-up actor Jerry O'Connell, but with a lumberjack beard and shock of hair like an unmowed lawn.

Well, that depends on what you mean by "insane." Doctors, certainly, would call it inadvisable. A seriously overweight person who embarks on any kind of strenuous physical activity could place dangerous stresses on his joints and heart, said Samuel Klein, director of the Center for Human Nutrition at Washington University in St. Louis.

And such activity is especially worrisome in an area of environmental extremes, without someone to support him, Klein said. Even if he weighed 100 pounds, "walking across a desert without someone standing next to him with an umbrella and a fan and Gatorade might really be a problem."

Vaught, meanwhile, has been almost completely on his own. For the first few days after he set off from the Pacific Ocean, his wife, April, would pick him at up the end of the day to bring him home to sleep at her mother's house, where the family is staying. Soon, though, he had gone far enough that he had to start camping; now he has not seen his family in three weeks.

Now and then a friend catches up with him for a few hours or days. But mostly it is just him and his 75-pound pack and the left-hand shoulder of the road.

Since he entered the desert, he has had to cut back his walking hours dramatically. Now he walks from about 5:30 to 8:30 in the morning, when he has to stop and find shelter -- preferably in a store or post office if one is around, but usually under a bridge or in a culvert or bush.

He will sit there for 11 or 12 hours, until it is cool enough to walk again for a few hours. Just sit there. "I'm too bored to read," he says, or even take in the landscape more than he already has.

"It's beautiful for the first hour or so," he said. "And then it loses its impact."

Yet on the question of "insane," the responses to the Web site chronicling his journey -- www.thefatmanwalking.com -- appear to be running heavily against. On a recent afternoon, Vaught accepts a ride from a reporter 35 miles down the road to a public library, where he checks his e-mail.

There is one from a 37-year-old guy preparing to run his first marathon. A 62-year-old woman planning to hike the Pacific Crest Trail. People in such places as St. Louis and Altoona, Pa., offering food and water and a place to stay when he comes their way. Overweight people across the country begging to know Vaught's daily mileage so they can match it at home.

Only a few call him crazy. Almost all say what an inspiration he is.

It is something to think about, on those lonely and terrible days on the road, he says. "Now I have all these people not to let down."

A Troubled Past

Even at 400 pounds, he never thought of himself as a fat guy. Perhaps because he never used to be, perhaps because it was the least of his problems.

Fifteen years ago, he was the fun guy. A slew of girlfriends, a bunch of friends, a witty streak so hot he would gladly take the stage at a comedy club open-mike night. Then one evening in October 1990, driving too fast against the setting sun, he struck and killed an elderly couple crossing the street.

The accident sent him to jail for 10 days, ruined him financially and dulled him emotionally. When he started to put on the weight, he just didn't care. He remembers little about the next three years.

After the birth of their first child, he grudgingly went to therapy, just so April would know she had done everything she could in case he killed himself. Medication snapped him out of his depression. But life didn't get any easier. A few businesses failed, and they went deep in debt on a house. And the weight, he realized, was bringing him down.

"There's nothing appealing about fat people," he says bluntly. "You can't impress them when you're fat." His jobs steadily declined in quality. In March he said he walked away from the latest, managing a muffler repair shop, after the owners sniped about him sitting down too much at work.

One morning that week, he turned to April in bed. "I ought to walk across the U.S.," he said. Once he left, he added, it would be hard for him to quit.

"If that's what it's going to take," she replied.

So he has a lot to think about as he walks. About the anger he carried around so long, and how pointless it seems now. About how accepting help from people doesn't shame him anymore, now that he sometimes has to ask strangers for water. And about the value of living in the moment, of just surviving that next stretch of road.

"It has nothing to do with weight anymore," he says. "It's about getting back to the person I was."

Vaught gets the reporter to drive him back west to the outskirts of Peach Springs, near where he stopped walking. At 5 p.m., it's still 92 degrees, and he looks for a place in the shade where he can wait.

He sees it about 50 yards off the highway, a culvert over a now-abandoned part of the original Route 66. "This is good," he says. He lifts his pack onto his shoulders. The strap holding it to his still-massive gut now has eight inches of excess past the buckle, compared with two inches when he began.

He manages to heave his body over the guardrail and starts walking. By the time the car has turned around and driven past again, his 350 pounds have vanished into the desert.

Staff writer Catharine Skipp contributed to this report.

Steve Vaught, on Route 66 near Peach Springs, Ariz., decided as he neared his 40th birthday that he needed to slim down to be alive for another decade.Vaught has lost about 50 pounds since April 10.