Believe it or not, no recommended dietary allowance (RDA) for fat has ever been set. So how are we to know how much fat to eat? What's too much fat in the diet and what's not enough?

If you're an avid food-label reader, you're most likely aware of the suggested "Percent Daily Values," and food labels do say the PDV for fat is 50 grams each day, for someone who's eating 2,000 calories a day.

Many health experts agree that keeping our total fat intake to about 30 percent of our daily calories is heart-healthy. Calorie-healthy, too, since fats contain 9 calories per gram, versus the svelte 4 calories per gram for carbohydrates and protein. (By the way, a teaspoonful or "pat" of butter or margarine contains 45 calories.)

Other researchers, however, argue that 30 percent fat in your diet is too high; this camp suggests we get no more than 25 percent of our calories from fat. This advice might be especially important for women who have breast cancer or a strong family history of breast cancer: One study cited a 20 percent decrease in the risk of breast cancer in women who got just 25 percent of their calories from fat.

Too little fat in the diet

It's also important to know when you're getting too little fat. Not getting enough can leave a woman in hormonal melt-down (as in a menstrual period that's vanished) and it leaves everyone at risk for deficiencies of fat-soluble vitamins (A, D, E, and K) and essential fatty acids (fats your body can't make on its own).

And did I mention that your hair, skin, and nails will look like sin if you're not eating enough fat? Eat more and you might find you've got more verve and vitality.

Recommendations about fat

• Aim for less than 1/3 of calories coming from fat (food labels help, or online food logs).
• Strive to get most of your fat from monounsaturated fats (in olives, olive and canola oils, and nuts) and get essential fatty acids from the polyunsaturated oils in safflower seeds, sunflower seeds, and corn.
• Try to steer clear of saturated fats (no more than 7 percent of your calories) and avoid trans fats entirely.
• At a restaurant, order one of the healthier meal options, or split a meal or appetizer.
• At home, use a non-stick cooking spray along with a small amount of oil (e.g., 1 tablespoon of olive oil and plenty of non-stick spray).
• Switch from regular to light butter -- tons of flavor with half the fat and calories. A butter spray also adds flavor without calories.
• Eat fatty fish. A 4-ounce (cooked) serving of Atlantic salmon has 14 grams of fat (the equivalent of about 3 teaspoons or pats of butter) but less than 3 of those grams are saturated.