Jack Sprat would like that -- less fat in 'choice' beef

First it was skim milk. Then came the rise of the salad bar. Now, there may soon be an addition to the ranks of less-filling foods -- ''Light Beef.''

It wouldn't really be a new product. Instead, the US Department of Agriculture is proposing to reduce its standards for marbling -- the bits of fat , speckled through cuts of beef, that provide flavor and connote quality.

Progressively leaner levels of meat would qualify as USDA ''prime,'' ''choice ,'' and ''good.'' The voluntary grading system, begun in 1927, rates about three-fourths of the beef sold retail to consumers.

The change has been sought by cattlemen, who stand to save about $300 million annually in feed and related costs, according to USDA estimates. It may also reflect a trend of consumers asking for leaner cuts of meat, which are easier on both their diets and, they hope, their pocketbooks.

''A leaner beef is big (more popular),'' says Thomas Smith, research director at the Community Nutrition Institute. But Mr. Smith maintains that the new rating system ''creates a situation very detrimental to consumers.''

He argues that altered standards would confuse the shopper who likes marbled beef, cause hefty new administrative costs for the USDA, and force retailers to spend money on new marketing campaigns. In addition, he says, it means just plain lowered quality.

''It doesn't do what it intends to do,'' he says. ''There are only very speculative benefits.''

If consumers are after less-filling beef, he says, why not just give them a whole new grade? Smith proposes changing the ''good'' grade to ''choice light.''

''There'll be more incentive for cattlemen to market'' the cheaper-to-raise category then, he says. ''It'll achieve every one of the goals with none of the drawbacks.''

Over the past several years, rising costs and falling prices have been squeezing beef producers. Casting about for ways to ease the pressure, the National Cattlemen's Association last year petitioned the USDA to modify existing beef quality standards.

''The consumer is seeking a leaner product,'' says Thomas Cook, an association spokesman. ''And we feel changes would allow the industry to feed cattle for shorter periods of time'' and still produce beef for the more desired and profitable higher grades.

The USDA proposal, published recently in the Federal Register, would reduce the marbling requirement for ''prime'' from ''slightly abundant'' to ''moderate.'' This would result in twice as much beef qualifying for the highest-quality stamp, the USDA estimates .

The minimum requirement for ''choice'' would go from ''small'' to ''typically slight.'' The ''good'' grade would similarly be lowered.

But those definitions mean more to meat inspectors than to a shopper looking for a flavorful chuck roast. Will consumers be able to tell the difference?

''Meat in every grade will be a bit lower in average palatability,'' says Herbert Abraham, a USDA meat-marketing specialist. ''But the change would be so small you'd never tell the difference.''

And ranchers would save money. USDA believes the changes would cause cattle to be fed an average of 7 days less before being taken to market -- a saving in grain of $217 million annually.

But the change would also mean that 1.4 to 1.8 percent fewer pounds of meat would make their way to supermarket shelves. Supply and demand would keep retail prices from sinking along with production costs.

''We're not guaranteeing there will be savings for the consumer,'' says Tom Cook of the cattlemen's group, ''but hopefully there will be some.''

Much of the proposal's fate will be determined by consumer reaction. The USDA is holding a series of hearings, beginning Feb. 9 in Salt Lake City, on the new standards in general and what shoppers think about lighter beef in particular.

''It is anticipated,'' says the proposal, dryly, ''that there will be widespread interest in the proposed changes.''