William Laste thinks nothing of driving more than 400 miles round trip to buy groceries, or of supplementing his shopping with fiddlehead ferns and dandelion greens gathered in fields near his home.

In this mountainous outpost of 870 people along the Canadian border, good food at fair prices is hard to find. There are no supermarkets, and the community's two convenience stores offer little fresh produce and plenty of high prices.

Laste's fixed income cannot accommodate $2.99 for his favorite cheesy crackers. He gets around it by combining shopping with monthly visits to friends in cities to the south, where the same crackers cost half the price.

"Up here, you're so far out they've got you over a barrel," the retired plumber, 69, said recently. "I couldn't afford to shop up here."

Such is life in "food deserts," increasingly common rural -- and sometimes urban -- areas where supermarkets with healthful and affordable food are many miles away.

For people such as Laste, who have the vehicles, time and patience to go the distance, it is an inconvenience. For the poor and elderly, it can mean stocking the refrigerator with the pricey, fatty fare of gas station convenience stores.

"It's going to be more chips and canned and processed foods, which just play into high rates of obesity, diabetes and other fat-related diseases," said Andy Fisher, executive director of the Community Food Security Coalition in Venice, Calif.

"It's kind of a real perverse irony that the people who have the least are paying the most."

The term "food desert" was coined more than a decade ago in Britain, where it was used to describe the phenomenon of supermarkets withdrawing from cities to build larger stores on the outskirts.

Few formal studies have been done in the United States, but sociologists and social service workers believe research eventually will show that life in food deserts is financially, mentally and physically costly.

The majority of U.S. food deserts are rural areas, but researchers say a large number of people also are affected by a fairly small number of urban areas with poor grocery access.

Experts say the grocery landscape in the United States has not always been this way. Not so long ago, most communities had mom-and-pop grocers. That was before the suburbanization of shopping.

Americans want bargains, and they want them in big stores. But big stores do not fit in crowded inner cities, and small towns cannot support them. So supercenters grew up in the suburbs, where land is less expensive and shoppers are plentiful.

While making food and other products cheaper than ever before for millions of people, those massive stores siphon shoppers away from smaller markets in surrounding communities and city centers, forcing many to close.

During the 1950s, more than half of all grocery stores were mom-and-pop operations. Today, just 17 percent are, said Walter Heller, research director for Progressive Grocer magazine.

For 17 years, Jerry and Dot Nering have run a small shop in Weld, Maine, a remote town of 400 people. In its heyday the shop was stocked with meats, cheeses and produce, and shoppers swapped gossip around a wood-burning stove.

Today, many of the Weld General Store's shelves are bare and customers only trickle in. The Nerings blame the two Wal-Mart Supercenters that have opened within 20 miles of their shop.

Business is so bad that the Nerings struggle to get suppliers to deliver to their western corner of the state.

"Our cost is higher than Wal-Mart sells for, so you can't compete," Jerry Nering said.

The U.S. Department of Agriculture estimates that the price of groceries is on average 10 percent higher in food deserts than at suburban grocers. In some locations the premium is far higher. A gallon of milk in Concord, N.H., a city of 40,000 people with seven supermarkets, recently cost $2.69. The price is $4.25 about 120 miles north in Milan, a town of 1,300 with no supermarkets.

The definition of food deserts is relative. In cities, where fewer people own automobiles, it might mean having to walk a mile, said Troy C. Blanchard, a sociologist at Mississippi State University. In rural communities, it could mean a 30-mile drive.

And public transportation -- a rarity in rural areas, anyway -- does not always help.

"Imagine trying to get a week's groceries if you have a couple of kids, carry that onto a bus, transfer it to a subway and carry it home," said Blanchard, one of a handful of people studying the food desert effect in the United States.

Using census and other federal data, Blanchard charted supermarket access nationally. He found it was the worst in the West, where 44 percent of the average county's population has poor access to grocers.

The Midwest followed with 34 percent, the South with 24 percent and the Northeast with 10 percent.

"Sometimes the food pantries have a better selection of food than the grocery store in town," said Dawn Girardin, who works on hunger and other welfare issues at Western Maine Community Action in East Wilton, Maine.

For Lorraine Karchenes, who lives with her husband and 4-year-old son in Eustis, Maine, the inability to get organic and specialty foods in their town of 715 people forced her to look both farther afield and closer to home.

For vitamins and wheat-free products for her son's allergies, Karchenes, 32, turned to the Internet. For fresh produce, she turned to the 90 acres of farmland that stretch out behind her home.

The farming has gone so well that others now seek out her produce. A small sign at the end of her driveway advertises what is in season, and the local shop recently began selling some of her vegetables.

But for most working families and the elderly, few of whom have experience growing and storing food, farming is not practical, said Thomas Lyson, a sociologist at Cornell University who studies food deserts.

"Even farmers tend not to grow their own food," he said. "What are you going to do, have a cow so you can milk it 12 months a year? We're not asking to become peasants again."

Few people think the grocery industry intentionally puts food out of reach of rural shoppers; supermarket chains locate their stores where it makes the most financial sense and they can cater to as many people as possible.

Jim Harrison, president of the Vermont Grocers' Association, said the industry is not actively addressing the food desert problem, but supermarket chains always are searching for ways to serve more customers.

Wal-Mart spokeswoman Daphne Moore said her company, which has 1,500 supercenters nationally, has a history of catering to underserved regions and is looking to build more urban stores to help with grocery access in those areas.

Some grocers, as well as senior homes and social service agencies, have experimented with shuttles that travel to the stores. These are not always cost-effective or efficient, especially over long distances.

Heller notes that the fastest-growing segment of the grocery industry is "limited assortment shops" -- stores with perhaps 1,500 items, similar to Trader Joe's.

These shops require less real estate and fewer customers. They might help alleviate urban food deserts, but Heller acknowledges that most are not likely to be placed in rural communities.

Fisher thinks the blame -- and responsibility for fixing the problem -- goes to local and state governments, few of which have recognized supermarket access as a basic need.

"They haven't really focused on food as being a public issue," he said. "Planning departments aren't out there drawing maps of where there are food deserts."

Jerry Nering says he struggles to compete against large supermarkets.Lorraine Karchenes was unable to buy organic produce in her town, so she decided to grow her own.William Laste looks through what little fresh produce is stocked at his local store in Pittsburg, N.H.