Fatphobics, a subspecies that includes greasephobics, are being invited by Hardee's to try its new Lean 1 hamburger. The North Carolina firm, which has 3,300 outlets, is claiming that its quarter-pound sandwich with a hunk of cow flesh is 10 percent leaner than McDonald's and 50 percent leaner than Burger King's Whopper.

Hardee's is sending messages. To competitors: Eat your hearts out. To the public: Eat our hamburgers to your hearts' content. A third message -- unspoken, true and factual -- is the only one worth remembering: Food companies can get religion, of a sort.

The new faith is nutrition, the conversion involving a shift from selling taste to selling health. Placed against decades of let-them-eat-fat resistance, this is progress, equal to the other astounding marketplace conversion currently on view -- automobile companies lusting for the safety market via air bags.

Hardee's announcement of a low-fat hamburger is a marketing strategy that says that the junk food at its joints is less junky than the junk at the other joints.

In this corporate food fight, which involves a $65 billion annual market, Hardee's is another company heeding what independent nutritionists and public interest groups have been arguing since the early 1970s: Fat kills. About 800,000 people die annually from diet-related diseases. Fast-food operations still invite customers to live off the fat of the land, but in 1990 they are selling much less disease than in 1980. Salads are now present. In several chains, vegetable oil has replaced animal fat for frying. Some offer grilled, not fried, chicken. McDonald's has reduced the fat content of milkshakes by 80 percent.

Fat City is not yet a ghost town, but yesterday's radicals are now welcomed on its Main Street. What Michael Jacobson of the Center for Science in the Public Interest has been arguing for 20 years -- malnutrition is too few of the right foods and over-nutrition is too many of the wrong foods -- is now the accepted wisdom. Frances Moore Lappe's 1971 "Diet for a Small Planet," which advocated high-protein meatless cooking, led her to co-found the Institute for Food and Development Policy in 1975, one of the country's most trusted sources for world hunger information.

Much of what Jacobson and Lappe were calling for was officially adopted in 1979 when the surgeon general said, "Americans would probably be healthier as a whole if they consumed ... less saturated fat and cholesterol." In 1984, the American Cancer Society finally emerged from the dark by urging the public "to cut down on fat intake." With vegetarians and vegans excepted, the average American diet takes about 40 percent of its calories from fat. Citizens truly serious about avoiding heart disease or cancer cut it down to 20 percent or 10 percent.

As leaner times arrive, the newest converts appear eager to be the loudest. The Beef Industry Council and Beef Board, which claims to market "real food for real people," is coming on as leader of the health-food movement. Its current ad campaign tells of "the skinniest six." These slabs of steer corpses -- round tip, top loin, top round, eye of round, tenderloin and top sirloin -- "are surprisingly lean and low in calories."

It's no surprise at all. The cuts of meat in the ads can be called lean and low because they are trimmed before cooking and weigh only three ounces. That morsel isn't much real eating for allegedly real people. The beef sellers' "skinniest six" aren't for those with lean incomes. Sirloin and the rest are among the most expensive cuts at the meat counter, with cheaper and excessively fat hamburger being the typical buy.

The beef industry's incredible call from fantasy land to eat meat and be healthy is matched by Mars Inc., another seller of fat. In a letter to The Washington Post about the "significant nutrient contributions" of M&M's chocolate peanut candies, a Mars vice president for "scientific affairs" states that that product, as well as M&M plains, surpasses apples in protein, calcium, zinc, iron and other goodies. Like the beef pushers, the man from Mars left out the negatives. M&M's are high in sugar and fat, with one rotting teeth and the other clogging arteries.

Posturings of junk-food companies represent a new brazenness. After decades of indifference to health, they pose now as stomach defense leagues. From Hardee's to M&M's, hard swallowing is coming.