Quick: How often do you look at the nutrition facts on the products you buy?

If you said frequently, you're being smart about your health: Adults who read food labels slash twice as many calories from fat as those who don't give them a look, according to a study published in the Journal of the American Dietetic Association. But that doesn't mean you have to read every line, every time you shop. Whether you want to gain energy, protect your heart, lose weight, or more, you can make the best choices for your objective by scanning a few select pieces of information. Here's where to look depending on your health goal, plus the spot that deserves a second glance.

Scan the ingredients list for the word whole before grains like wheat, corn, barley, rye, and rice. (Millet, amaranth, quinoa, and oats are whole grains, too.) Whole grains sustain energy because they keep blood sugar stable. Refined carbohydrates (such as white sugar and flour) cause big spikes and drops in sugar levels that can leave you feeling drained, says Tara Gidus, RD, a spokesperson for the American Dietetic Association.

Daily goal: At least three 1-ounce servings of whole grains

Look for 10% Daily Value (1.8 mg) or more per serving. Without enough iron in your blood, your cells don't get oxygen they need, and that causes fatigue, says Nancy Clark, RD, author of Nancy Clark's Sports Nutrition Guidebook. It's especially important to add iron-enriched packaged foods to your diet if you don't eat red meat.

Daily goal: 18 mg for age 50 and younger; 8 mg for age 51 and older

Look for 1 g or less per 100 calories. (If the food has 200 calories per serving, it should have no more than 2 g of saturated fat.)

Most of the cholesterol in your blood doesn't come from high-cholesterol foods; it's actually made by your body — and the culprit is saturated fat. The more you consume, the more cholesterol your body makes. So even if you see cholesterol free stamped on the package, the food may still be a bad choice if it's loaded with saturated fat. Of course, you can still indulge in a little saturated fat-filled ice cream or cheese now and then — you just have to plan for it. A ½-cup scoop of your favorite flavor, for example, may have 13 g! Save it for a splurge and shoot for a minimal amount of sat fat the rest of the day.

Daily goal: No more than 10% of your daily calories (for a 1,600-calorie day, that's 17.5 g of saturated fat)

Look for 0 g in the nutrition facts and no hydrogenated anything in the ingredients list

Trans-free products are easier to find these days, but manufacturers can still claim "no trans fats" if there's less than 0.5 g per serving; eat two servings and you may get nearly 1 g of trans fat — enough to raise your "bad" LDL cholesterol and worse, reduce your "good" HDL cholesterol. That's why you have to scan the ingredients list, too: "Don't eat it if you see the word hydrogenated," says David L. Katz, MD, MPH, director of the Yale Prevention Research Center in New Haven, CT. "Look for trans-free products that list liquid canola and olive oils instead."

Daily goal: As close to 0 g as possible

Look for it touted on the food package, not on the label

A slew of products, including cereal, eggs, and juice, are fortified with omega-3 fatty acids, but you won't find any values for them listed on the product nutrition label; instead, a statement, usually found on the front of the package, will say how much of this fat the food contains. A study done at the Rush Institute for Healthy Aging in Chicago showed that older adults who got omega-3s from at least one fish meal a week were 60% less likely to develop Alzheimer's disease than those who rarely or never ate fish.

Daily goal: 1,000 mg

Make sure most (about three-quarters) is poly- and/or monounsaturated fat. (If a food has 10 g of total fat, 7 to 8 g should be unsaturated.)

Foods that are high in polyunsaturated and monounsaturated fats (such as oils and margarines, for example) list both values on their labels — just add them up to see if they equal about three-quarters of the total fat count. (If the label only lists saturated fat and trans fats, subtract them from the total fat count to get an unsaturated count.) It's worth the effort: Researchers at the Rush Institute also discovered that unsaturated fats may defend against Alzheimer's disease. People who ate about 24 g of monounsaturated fat per day had an 80% lower risk of disease than those who got only 15 g, they found. A diet that's higher in unsaturated fats improves your cholesterol profile, and that can help keep brain cells healthy, too.

Daily goal: Total fat less than 30% of your daily calories, with about three-quarters of that coming from unsaturated fat.

Look for low counts and large servings

It's the golden rule: Take in 500 fewer calories each day, and you drop 1 pound per week. So looking for low-cal meals and snacks makes sense. But when you're standing in the supermarket reading the back of a snack-size box of raisins, for example, how do you know if 130 calories is too high or low? The key is to compare similar types of food and pay attention to serving sizes. You get 1.5 ounces of raisins for those 130 calories, but a pineapple snack bowl offers 4 ounces of fruit for only 54 calories. Considering the servings per container helps keep you on track, too: Most soup brands contain two servings per can, so double the calorie count if you normally eat an entire can in one sitting. The same goes for beverages: A 20-ounce soda bottle contains 2 ½ servings; at 100 calories per serving, you consume 250 if you drink the whole thing.

Daily goal: About 1,350 calories per day if you are average height and not very active; up to 1,800 if you are tall or if you exercise three or more times per week

Look for 3 to 5 g per serving

High-fiber foods help you stay slim because they fill you up with fewer calories and slow down digestion so you feel fuller, longer. An analysis of research published in Nutrition Reviews showed that people who added 14 g of fiber to their diet more than 2 days a week lost about 1 pound a month.

Daily goal: At least 25 g

Look for 20 to 30% Daily Value (200 to 300 mg) per serving. Adding calcium-rich foods to your diet is better than simply relying on supplements, says Robert P. Heaney, MD, a professor of medicine at Creighton University Medical Center. The interaction of nutrients, such as protein and magnesium, helps your body use the calcium better. And postmenopausal women who get most of their calcium from foods have higher bone density than those who just pop calcium pills, says a new study published in the American Journal of Clinical Nutrition.

Daily goal: 1,000 mg for age 50 and younger; 1,200 mg for age 51 and older

Look for at least 10% Daily Value per serving. (That equals 40 international units, or IU.) Typically, only foods that are fortified with vitamin D — such as milk, some ready-to-eat breakfast cereals, and orange juice — have it listed on the food label. (Natural sources include wild-caught salmon, sardines, and whole eggs.) This vitamin helps transport calcium from the digestive tract into your blood. Without D, your body may only absorb up to 10% of dietary calcium.

Daily goal: 400 to 800 IU for age 49 and younger; 800 to 1,000 IU for age 50 and older