Drive across America, and you'll see one fast-food restaurant after another: McDonald's. Burger King. Sonic. Taco Bell. K-F-C. Wendy's. Hardee's. Long John Silver's. Dairy Queen. Arby's. Jack in the Box. Popeyes. Subway. Quizno's. A&W. Whataburger.

There's even a chain that's aptly named Fatburger, plus assorted pizza joints.

Though some of these fast-food places now offer a few low-fat items, the big sales and profits are in hamburgers, French fries, milkshakes, fried chicken, and greasy pizza -- the very things that the U.S. surgeon general says are fueling America's obesity epidemic. Which makes you wonder, as you drive past one burger place after another, why someone hasn't made a billion dollars by opening fast-serve restaurants that offer nourishing, expertly prepared, low-fat meals. Why not, indeed, when we can find tasty baked chicken, broiled fish, veggies and the like at sit-down restaurants and upscale grocery stores? According to Bryan Elliott, a food-industry analyst at Raymond James and Associates, some entrepreneurs have tried this idea -- and gone bankrupt. That's because the ingredients and technology to mass-produce nutritious food are much more costly, and it's hard to find low-paid line cooks who can quickly prepare low-fat, but interesting, dishes. Bryan Elliott says chains serving healthful fast food WILL evolve, once costs come down or Americans get used to the idea of ordering, and paying a bit more for, a quick lentilburger and salad instead of cheeseburger and fries on the road.