The day begins with a sunrise jog or walk in the Sierra Madre hills. Depending on how early you get up, you might also be able to fit in a class of wake-up exercises before breakfast.

There is time for three more exercise sessions before lunch, and three more between lunch and dinner. There is plenty of opportunity for walking because the buildings have deliberately been set far apart.

Rancho La Puerta, on the Baja California Peninsula just south of the border, is a vegetarian fitness resort that began 37 years ago as a vegetarian health spa. In between it was a fat farm when those were popular. Gradually it has evolved into what it is today, a place for men and women to lose weight and become fit.

It was planned as an experiment in living with organically grown foods free of chemical preservatives and of saturated fat. Tobacco and alcohol were also off limits. In 1940 that was pretty far out. The rest of the world is beginning to catch up. Today vegetarianism continues to gather converts. Few people think they are strange. Some people think they even might have found the right ticket to a longer life.

The low-calorie, low-sodium, low-cholesterol diet at the 40-acre ranch is lacto-ovo vegetarian, made up of lots of whole grains, fresh fruits and vegetables with some eggs and milk products. It is satisfying, nutritious and best of all good tasting. Much of the food is organically grown; everything is prepared in the small kitchen at the ranch including the famous Tecate, or Ranch bread of whole wheat flour and honey.

Most of the guests are there not only to tone up, but to slim down. The standard menu is 1,000 calories a day, which ensures safe weight loss. For those who want to maintain their weight, additional dishes are offered. All is attractively served, buffet-style in a dining room that reserve one small area for those who cannot give up cigarettes. It's called Nicotine Nook.

When the weather is warm enough, as it is most of the time, people eat outside under the grape arbor.

The grape arbor and the many grape vines that grow around the ranch provide the sparkling grape cider that was once considered a curative. Today, it is available to those who want to try it and fits somewhere between grape juice and fermented grapes or wine.

Back in the days the grape cider was considered a curative, Rancho La Puerto, which was set up by its present owner, Deborah Szekely Mazzanti, and her former husband, Dr. Edmond Szekely, was like a commune where people pitched their own tents and helped garden and cook to earn their keep. Over the years the ranch has become far more luxurious, with individual adobe casitas (little houses), each decorated in rustic Mexican style, accommodating the 110 guests.

There is tremendous emphasis on physical fitness, but unlike Mazzanti's other spa, the more expensive and more regimented Golden Door in Escondido, Calif., guests are left to their own devices when it comes to determining their program. Some choose a vigorous program, partaking of every single exercise class; some intersperse the exercises with sauna, massage, facials, some just sit around.

But those who are determined to lose weight can, and relatively easily, unless of course they sneak off to the little town of Tecate where they can gorge themselves at EI Passetto (Mexican, American and Italian food), preferably on the superb Mexican food.

But there really is no reason to seek a change from the ranch meals: they are varied, well-prepared and delicious.

A typical breakfast is a half-slice Tecate bread grilled with cheese, papaya with lime or muesli, a cereal of oats mixed with figs, grated apple and hazelnuts, served with skim milk.

Lunch might be peanut butter soup, crudities with a curry-flavoured yogurt dip, spinach pie (without the crust) plus fruit.

At dinner, soup is often served as a first course, followed by a salad with a yogurt-blue cheese dressing, a mixed vegetable quiche with eggs and cheese, and a fruit dessert, sometimes in pudding form, sometimes fresh with a topping, sometimes even a pie or custard.

A condiment table always holds bowls of green onions, cilantro (Chinese parsley, which has a much more pungent flavor than parsley) and a marvelous Mexican salsa, or hot sauce made with tomatoes, hot chilles, green onions and cilantro. These add zesty flavor to the meals.

Curiously, just when more and more people are becoming vegertarian, Rancho La Puerta has decided to yield to numerous guests who are not yet prepared to "go all the way." For years there was no meat, fish or poultry. Today fersh fish is served twice a week; tuna fish once. Of course you don't have to eat it.

For further information write to Rancho La Puerta, Tecate, Calif. 92080.

The following recipes from chef Juan Murato have been adapted for home preparation. TECATE BREAD (2 loaves) 1/2 cup honey 3 1/2 cups warm water 2 tablespoons yeast 1 teaspoon fennel seeds 1 teaspoon caraway seeds 8 cups whole wheat flour 1 teaspoon salt 3/4 cup vegetable oil

Mix honey and water. Dissolve yeast in mixture. Let rest 10 minutes. Add fennel and caraway. Mix flour with salt and then stir into yeast mixture. Knead dough for 30 minutes, adding oil gradually as dough requires to keep from sticking. Divide into two and work each for a few minutes. Oil dough, shape into loaves and place in oiled loaf pans. Let rise 10 minutes, then place in 450 degree oven for 12 minutes. Lower temperature to 350 degrees and bake 1 hours; lower temperature again to 250 degrees and bake 1 hour and 15 minutes longer. Let bread cool on racks before removing from pan. SALSA MEXICANA

(A piquant relish used extensively with Mexican foods)

(Approximately 2 1/2 cups) 2 cups finely chopped, peeled and seeded tomatoes 1/3 cup chopped green union 1/3 cup chopped cilantro 1 clove garlic, minced 2 canned or fresh hot chilles, finely chopped about 2 tablespoons 1 teaspoon salt 1/4 teaspoon dried oregane

Combine all ingredients and chill for sereral hours. Serve with tostadas, over cottage cheese, with guacamole, or just as a side dish. TOSTADAS

(4 servings, one tortilla each) 2 tablespoons oil 4 corn tortillas 1cup cooked pinto beans, mashed 8 thin slices tomato 4 thin slices Spanish onion 1/4 cup grated Romano cheese 1 small ripe avocado, cut in 8 slices 1 cup finely chopped romaine lettuce 4 tablespoons or more Salsa Mexicana (see recipe) 4 black olives, sliced

Heat oil; fry tortillas on both sides until crisp and golden. Pat with paper towels to remove surplus oil. Spread 1/4 cup mashed beans on each tortilla; add 2 slices tomato and one slice onion. Sprinkle each with one tablespoon cheese; add 2 avocado slices, 1/4 cup lettuce, one tablespoon or more salsa and one olive. SPINACH PIE

(2 pies 8 servings) 1/2 cup chopped scallions, white and green parts 2 tablespoons oil 2 pounds fresh spinach, stems removed, washed dried and chopped 1/3 cup finely minced parsley 1 teaspoon dill weed 1/2 pound feta cheese, crumbled or creamed cottage cheese 5 eggs, beaten Whole wheat pastry crusts (see recipe)

Saute scallions in hot oil unit tender. Combine remaining ingredients and add scallions. Spoon into pie crusts and bake at 350 degrees for 30 to 45 minutes or until eggs are set. Serve hot or warm. WHOLE WHEAT PIE CRUSTS

(Makes 2 crusts) 1 1/2 cup whole wheat pastry flour 1/2 cup rye flour 1/4 teaspoon salt 3 tablespoons oil 3 tablespoons sesame tahini 1 tablespoon sesame seeds 1/3 cup or more water 1 egg white

Mix flours with salt. Add oil, tahini and sesame seeds and mix with hands to distribute throughout flour. Add water, a little at a time, kneading until dough is workable. Divide dough in two and roll each portion out into a circles to fit into a 9-inch pie plate. Brush bottoms with egg white and prick bottom and sides with fork. Bake at 400 degrees for 8 minutes. Cool and fill with spinach mixture. VEGETABLE CRUSTLESS QUICHE

(4 servings) 1 tablespoon oil 1 medium onion, thinly sliced 1 garlic clove, minced 1 green peper, chopped 1 cup sliced cauliflower 1 cup sliced mushrooms 1 cup fresh, frozen or canned corn 1 1/2 tablespoons drained, chopped pimiento 6 eggs, beaten 3/4 cup grated cheddar cheese 3/4 cup grated Monterey Jack cheese Salt to taste 1/2 teaspoon each cumin and marjoram 1/3 teaspoon curry Paprika for garnish

Heat oil in skillet over medium heat. In hot oil lightly saute onions, garlic, pepper, cauliflower and mushrooms. Then cover and cook over low heat for about 5 minutes longer. Stir in corn and pimiento. Then add eggs, cheese, salt, cumin, marjoram and curry. Spoon into greased shallow 2 quart casserole; sprinkle with paprika and bake 45 to 50 minutes at 325 degrees or until eggs are set. YOGURT FRUIT BAVARIAN

(6 one-cup servings) 2 packages (tablespoons) unflavored gelatin 1/2 cup fruit juice (orange, pineapple or apple) 4 eggs, separated 2 cups chopped fruit (strawberries, apples, blueberries, bananas) 1 1/2 tablespoons honey 1/4 teaspoon grated lemon peel 1/4 cup lemon juice 2 cup plain yogurt

Mix gelatin in juice to soften. Dissolve over low heat or over hot water, stirring. Cool. Beat yolks; stir in fruit, honey, lemon peel, juice and the gelatin mixture. Add yogurt. Beat whites until stiff. Fold into yogurt mixture. Pour into sherbet glasses and chill. Garnish with fresh mint leaves. YOGURT SAUCE FOR FRUIT

(About 1 1/2 cups) 1 1/4 cup plain yogurt%3 tablespoons honey 1/3 teaspoon each grated lemon and orange peel

Mix ingredients together and serve over fruit.