WHEN NOT cooking, most cooks are eating. To fill the gap between meals, there are two pastimes (three, if you count exercise; but few dedicated cooks do), cleaning up and reading.

Reading about food is more difficult than it seems because few "cookbooks" indicate any faith on the part of publishers that those who cook can read. Text is held to a minimum. You can search for inspiration, recipes stolen from another source or typographical errors, but seldom is there anything in these tomes to stimulate the mind. The food magazines aren't much better. Vicarious trips to far-off places with exotic recipes carefully shaped to domestic tastes are your reward for plowing past the advertisments. There is very little reflection or philosophy on the shorter, but more essential journey between plate and stomach.

The quintessential work in the latter vein was published more than 150 years ago. Jean Anthelme Brillat-Savarin's name isn't dropped in gastronomic circles these days as often as once it was. He's none the less wise, witty (or, at times, pompous); and M.F.K. Fisher's skillful translation of "The Physiology of Taste" makes him really accessible. There's a fancy edition found in secondhand bookstores or in a $4.95 paperback published by Harvest/HBJ.

Brillat-Savarin is best known for a series of one-liners he called aphorisms. Some of them, such as "Tell me what you eat, and I shall tell you what you are" or "The destiny of nations depends on how they nourish themselves," are being waved about today by nutrition activists. Others are less universal. For example, "A dinner that ends without cheese is like a beautiful woman with only one eye," hasn't been picked up by propagandists for the dairy industry.

Much of the fascination of "The physiology of Taste" springs from the author's remarks on the human body and its capacity to absorb and digest all manner of foods. It is remarkable, looking back to a period soon after the Napoleonic Wars, to realize how much was known, or at least how close the guesses were to "truths" science has confirmed since.

In Meditation 22, Brillat-Savarin presents the common approach in his time to curing obesity: "discretion in eating, moderation in sleeping, and exercise on foot or on horse back." He dismisses all three precepts with a trio of humorous shafts, then offers his own formula, that "a more or less rigid abstinence from everything that is starchy or floury will lead to the lessening of weight." He acknowledges the strain thus entailed, outlines mealtime choices and then turns to the season fast upcoming, summer.

"Every summer you must drink 30 bottles of Seltzer water," he writes, "a big glass in the morning, two before lucheon, and two more on going to bed. In general, drink white wines, light and acidulous ones like those of Anjou. Shun beer as if it were the plague (light beer hadn't been invented), and eat often of radishes, fresh artichokes with a simple dressing, asparagus, celery, and cardoons [chard]. Among meats choose veal and poultry: eat only the crust of bread; whenever you are in doubt, be advised by a doctor who agrees with my principles; and no matter when you may start to follow them, you will soon find yourself fresh, attractive, nimble, in good health, and ready for anything."

There is much more, of course. But we will ask the professor, as he dubbed himself, for only one other thought at this time. Writing about the high art entertaining with food had become in his time, Brillat-Savarin observed:

". . . no matter how studied a dinner plan nor how sumptuous its adjuncts, there can be no true pleasures of the table if the wine be bad, the guests assembled without discretion, the faces gloomy, and the meal consumed with haste."

His translator, M.F.K. Fisher, has given us some of the most readable prose about food composed in our own language. Her books are worthy bedtime, or mealtime, reading.

Of more specialized interest are small magazines or pamphlets about food or foodstuffs that spring up from time to time. I have three in mind.

The first has been published in England and bears the title "Petits Propos Culinaires." It is a collection of "essays and notes to do with food cookery and cookery books." In the first issue, which came out in February, Elizabeth David wrote about recipes for ice cream in the 18th century and on the authorship of the early 17th century work, "A True Gentlewoman's Delight." There is an extensive report on the technology of cooking in the British Isles before the use of gas. There is a reader request for recipes in verse.

Esoteric it is, but no more esoteric than the reason it has been published, to support "the Anglo-American Jubilee Appeal of the Royal National Lifeboat Institution." The first printing was only 500 copies. Two more issues are planned this year. The first was sold for a donation of 1.75 pounds (about $3.50) or more. Inquiries or orders may be sent to The Secretary, Prospect Books, 45 Lamont Road, London SW10 OHU.

A very specialized publication, produced much closer to home, is "Shelfish Digest." Robert H. Robinson, the editor-publisher, dwells in Georgetown, Del., and his most recent issue (at $1.50) instructs the reader in opening oysters with a beer can opener, how to dance at an oyster eat, and what is on view at the Chincoteague Oyster Museum. It also offers for sale a large array of knives and tools for shellfish, "crab-eating placemats," books, scallop shells, food products and gives a few recipes for clams, crab and shrimp.

For a copy, write to P.O. Box 469, Georgetown, Del.19947.

The third is "Garlic Times," also known as "The Digest of the Lovers of the Stinking Rose." The most recent one I received was published last April, but there is no reason to think the garlic lovers have thrown in the towel. They are eager to sell you Garlic Times, or "The Book of Garlic," or "Garlic, the Unknown Miracle Worker," among others. The issue I have talks about giant garlic, odorless garlic from Japan, a pilgrimage to La Vielle Maison in Truckee, Calif., billed as "America's first garlic restaurant." It discusses recent medical claims for garlic, tips for growing it and for using it as an herb.

Those who subscribe (a $10 check made out to LSR), are promised a free copy of "The Book of Garlic," and a lifelong subscription to Garlic Times. The address is Lovers of the Stinking Rose, 1043 Cragmont Ave., Berkeley, Calif.