Brother and sisters, friends and neighbors, hear my witness. I have been to the Other Side and I can tell you beyond a shadow of a doubt that, indeed, there is life after fat, cholesterol, salt and caffeine.

It is abundant, it is filling and it feels great.

Like most Americans, I have been aware for some years that a healthful diet should be low in fat, especially saturated fat, to help avoid heart disease; that salt can exacerbate high blood pressure in the salt-sensitive; and that overweight people are more subject to hypertension and heart disease. But, as an active fortysome- thing, I didn't have any of those problems, so I paid scant attention to the warnings.

Oh, I was careful to eat sensibly: lots of pasta, fruits and vegetables, little red meat, never frying food, not even stir-frying. I don't like soft drinks and don't crave sweets, though potatoes and cheese (of any kind) have long been my two favorite food groups.

Then, one day in March, my life changed. I learned my blood pressure was high enough to warrant medication and my cholesterol level was astronomical.

"This isn't fair!" I told my doctor. "I'm young, I'm good, I'm thin, I'm careful! I know a lot about nutrition -- I write about food, I can't stop eating it."

He peered at me over his glasses. "If you were a smoker, you wouldn't be here."

Of course, I haven't stopped eating. In fact, I'm nibbling as I write this -- on dried apricots. But I stopped drinking caffeinated coffee, stopped using any dairy products except no-fat varieties, mostly stopped eating meat, stopped using salt and stopped eating products with added salt. I stopped eating chocolate.

I suspect that most diet switches of this type are sudden: There is (for the lucky, like me) a diagnosis, or (sadly, for the not so) a heart attack. The latter was the case for a friend of mine in Kentucky, normally a hale and hearty golfer and gardener though he's pushing 80, who had a mild heart attack in January. He reported after leaving the hospital that he felt fine, but that his wife was "going crazy" trying to find something to feed him.

There are about a zillion "low-fat" cookbooks on the market these days, and they help. But it can be daunting to choose one. There are a number of risk factors in heart disease, and different people have different combinations. I have a hereditary tendency to high cholesterol and high blood pressure; other people may be overweight and have high cholesterol, or be diabetic and have high blood pressure.

The cookbooks tend to concentrate on particular areas. Some are mostly concerned with fat and calories and ignore sodium and caffeine; fine for weight loss, but no help for people with hypertension. Some pay no attention to sugar, which makes them useless for diabetics. Some offer ridiculously complex formulas for figuring out precisely how much of various things you are consuming.

And there are a lot of "low-fat," "no-fat," "lite," "reduced-calorie," "no-cholesterol," "low sodium" products these days. Some of the substitutes are pretty good -- no-fat yogurt, for instance -- and some are pretty awful -- like no-fat cream cheese. And some products are "reduced" from extremely high numbers -- like "low-fat" Cheddar cheese, which is merely 50 percent fat, instead of 75 percent fat. The new nutrition labels mandated by the FDA on virtually all products now are an important source of information.

So how do you pick your way through the treacherous shoals of dining without going aground in boredom or diving into the deep waters of indulgence?

Well, you might find a guide.

Pamela Lipis gathers four bottles of milk from the grocery shelves -- skim, 1 percent, 2 percent and whole -- and lines them up. "Now that the labels are all going to be uniform, you'll be able to tell how much fat is in milk. When you're thinking about 1 percent, you can easily make the assumption that, oh, 1 percent, that means it's 99 percent fat-free. And it is, but that means by weight. That doesn't really tell you the percent of calories from fat. You can look on here and see that there's 2 1/2 grams of fat. So using our trusty calculator . . . 2 1/2 times 9 gives us 22 1/2 calories coming from fat, so you divide that by 100 and that tells you this is 22 1/2 percent fat. . . . You're looking for foods that have less than 30 percent from fat, so 1 percent qualifies. And skim milk has no fat, so that qualifies." But -- the calculator goes into action again -- 2 percent milk is almost 38 percent fat and whole milk is a whopping 48 percent -- that's almost half fat.

Ms. Lipis is a registered dietitian who works in Heart Health programs at the Johns Hopkins Bayview Medical Center. Among her tasks is taking recovered heart patients on shopping trips to the local grocery. She gives each a calculator and leads them on a section-by-section tour, explaining what foods are low in fat cholesterol and sodium (in the produce section: "This is where you should be spending a lot of time."), showing them how to calculate the percent of calories from fat in a particular food ("There are 9 calories in a gram of fat, so you multiply the number of grams of fat by 9, and divide that by the total calories."), offering tips and suggestions to make heart-healthy shopping easier (in the canned fruit section: "applesauce is great, because when you're baking, you can substitute applesauce for the oil measure for measure").

People whose lives have been jolted by a heart attack don't always take kindly to suggestions that a complete lifestyle change is in order.

"Some of them take it on as a new adventure -- that there are foods out there that they have never tried, that there are recipes they've never tried, spices they've never had . . ." Ms. Lipis says. "Some are just the opposite. Some of them are like, well, you know, I've been eating bacon for 50 years of my life and, by golly, no one's going to tell me that I can't have bacon. You see them in all shapes and sizes, all combinations of motivation."

For the receptive, a trip to the grocery with her can be a revelation; a promise that life can still be full of wonderful things: five kinds of squash, five kinds of potatoes, pasta sauces that pass the less-than-30-percent-calories-from-fat test; frozen yogurt from Ben and Jerry's and Haagen-Dazs; yards and yards of spices and flavor extracts (almond! black walnut! anise! strawberry!); dozens of mustards and vinegars; dozens of kinds of pasta, all virtually fat-free; scads of fat-free and fat-acceptable cookies.

She's emphatic about what people should stay away from: In the cheese and deli meat aisle, she calculates the percent of calories from fat in "light" Cheddar cheese -- 50 percent -- and points out that the lunch meat labels proclaiming "97 percent fat-free" mean by weight, not by calories; and that many such products are still high in salt. "A lot of my patients in addition to watching their fat, they're watching their sodium. And it's very frustrating," she says.

Packaged foods such as "dinner helpers" and frozen dinners can be calorie-fat-sodium bombs, she notes. And when it comes to canned soup, "Avoid it like the plague," she says.

Breads, on the other hand, tend to have calories-from-fat figures in the teens. "The only issue that some people take with this, and they're very astute in noticing, is that a lot of them have a lot of salt." The newly wary shopper's old favorite, Dijon rye, has 110 calories, 15 calories from fat, no cholesterol -- and 340 milligrams of sodium per two-slice serving -- that's somewhat below the average in calories, somewhat above in sodium. But there are no-salt added varieties that have 20 milligrams to 30 milligrams of sodium.

People should remember to read ingredient lists, Ms. Lipis says, because they offer valuable information about how products are made. Ingredients are listed in order of amount: first item listed is the one used in the greatest amount. If salt is high in the list, there's probably a fair amount of salt in the product.

Canned vegetables are another place the salt-wary need to watch their step. But increasingly there are no-salt-added choices. "I have to give companies credit, they really have responded to consumer demand," Ms. Lipis says. She also notes that frozen vegetables may be a better choice: Foods designed to be shelf-stable for long periods of time need some preservative, and it's usually salt. However, with frozen items, the technique is the preservative, so such products may be very low in salt.

She has a simple method to tell people how to shop for meat: "With red meat, the redder it is, the less fat it has. With poultry, just the opposite is true: the lighter it is, the less fat it has." With fish, too, the lighter the color, the lower the fat. She pauses to pore over a posted list of nutritional information at the fresh fish counter. Sole, 10 calories from fat (none saturated), salmon, 60, 1 gram of saturated fat. For Marylanders, the most important item on the list is at the top: Blue crab, steamed, 90 calories, 10 calories from fat (none from saturated fat), 310 milligrams of sodium.

On the whole, it's a lot to remember. If you're thinking that the price of dietary vigilance is a big commitment of time in the grocery store, you're right. At least at first, it takes more time to read the labels and make the choices. But it gets easier once you've identified products you like. And feeling better can be a strong motivator.

At first I was haunted by thoughts of hot dogs and Big Macs. Of french fries and sour cream. Of Cheddar and Parmesan, Roquefort and Huntsman, Cheshire and cream cheese. But, as I explained to colleagues who commiserated over my dietary restrictions, when you think something is trying to kill you, you don't want it quite so much.

But now I've stopped missing all those high-fat, high-salt tastes I once thought I could never live without. I've become a believer. I tried some Cheddar the other day, and it tasted oily and salty. Coffee was a habit, not a lifeline.

I still have a few indulgences. English muffin halves with light cream cheese on Saturday mornings. And a small hot dog every time O's first baseman Rafael Palmeiro hits a home run when I am in the stands (though I'm considering switching to a less productive player -- maybe someone from another team).

And, oh, by the way: I've lost 15 pounds.

*

Here is one of my low-fat recipes. I eat it as a main dish; it would also be good as a side dish with baked chicken or grilled fish.

Rainbow couscous

Serves 4 to 6

1/2 cup onion, diced fine

1/2 cup green pepper, diced fine

1/2 red or yellow pepper, diced fine

1/2 cup tiny broccoli florets

1/2 cup mushrooms, chopped fine

1/2 cup carrots, diced fine

1/2 -1 teaspoon Herbes de Provence (see note)

1/2 -1 teaspoon cumin

1/2 -1 teaspoon cilantro

black pepper to taste

vegetable cooking spray

2 cubes frozen low-fat vegetable broth, or vegetable cooking water

2 cups water

1 cup couscous

Spray saucepan with cooking spray. Add onions, peppers, broccoli, carrots, and broth cubes and saute until onions are translucent, about 3-4 minutes. Sprinkle with half of each of the spices. Add mushrooms and heat through.

Remove vegetables from pan and keep warm. In pan, add cups water and remaining spices, bring to a boil. Add couscous and return to boil, stirring, then remove from heat. Stir in vegetables, cover and let sit 5-7 minutes. Fluff with fork before serving.

Note: You can use any combination of herbs and spices you like. Just be liberal with them. For that matter, you can use any combination of vegetables you like, as long as it adds up to about 3 cups.

Nutritional analysis: Per serving, 70 calories, less than 1 gram of fat (less than 1/2 gram saturated), no cholesterol, 58 milligrams of sodium.