When it comes to food labels, any dietitian worth her salt will tell you to pay attention to them. But not all the words on those labels  are created equal. Certain terms are backed up by law; others sound official but could mean anything—or nothing. Use this guide to translate the shelf talk and shop healthier with less hassle.

“Extra Lean”
Meat, poultry, or seafood labeled “extra lean” must meet strict requirements by the U.S. Food and Drug Administration (FDA). Every 100-gram serving (about 3.5 ounces) must have fewer than 5 grams of total fat, fewer than 2 grams of saturated fat, and fewer than 95 milligrams of  cholesterol. That amounts to a pretty small dent in your total daily fat allowance, which is about 55 grams if you eat 2,000 calories a day and get 25 percent of your calories from fat. (That intake is on the low end of the recommendations by the Centers for Disease Control and Prevention.)

Related: 24 Nutritious (and Tasty) Snacks

Smart shopping tip: If you’re cutting back on fat, extra-lean products are a better choice than those labeled “lean,” which can contain up to twice as much total fat (10 grams) and saturated fat (4.5 grams) per serving, with the same maximum amount of cholesterol.

“Low Fat” or “Reduced Fat”
Foods labeled “low fat” are required by the FDA to deliver fewer than 3 grams of fat per serving. “Reduced fat” means the food must contain at least 25 percent less fat than the original form.

Smart shopping tip: Low or reduced fat isn’t always the no-brainer option. Sometimes there are nutritional tradeoffs: Reduced-fat peanut butter, for example, may contain more sodium and sugar to boost flavor. Compare the nutrition facts before you buy.

“Made With Real Fruit”
“Real fruit” doesn’t always mean whole fruit. It might also mean fruit extract or juice, which could contain fewer nutrients or more sugar than the whole fruit does. And there aren’t any rules for how much of it needs to be in a box of toaster pastries, cereal bars, or other food for the package to carry this claim.

Related: 5 Healthy Low-Fat Snacks From the Grocery Store

Smart shopping tip: The only way to figure out the amount of whole fruit in a product is to examine the order of the ingredients, said Angela Ginn, registered dietician (R.D.), a Baltimore-based spokesperson for the Academy of Nutrition and Dietetics. Contents are listed in order of volume, “so don’t be impressed unless fruit—not fruit juice—is in the first three ingredients,” she said.

It means your chips, bread, cereal, or crackers contain two or more grains. But they’re not necessarily whole grains, which are a better nutritional choice than refined ones. With refined grains (such as white bread, or wheat breads that aren’t specifically labeled “whole wheat”), the nutrient- and fiber-rich parts have been milled out. The current recommendation is to make sure at least half your daily grains are whole.

Smart shopping tip: Whole-grain products list the word whole (as in “whole wheat” or “whole oats”) among the first few ingredients. You might also look for the Whole Grains Council’s symbol. Companies can pay to join this organization and receive its “stamp” on products that deliver at least 8 grams of whole grains per serving.

“99 Percent Fat-Free”
You may assume that means only 1 percent of the calories come from fat, but that’s not the case. Instead, “99 percent fat-free” means that  99 percent of a given weight of the food is fat-free, said Bonnie Taub-Dix, R.D., a New York City–based nutrition consultant and the author of "Read It Before You Eat It." So put on your math hat here: If the food weighs 100 grams, 1 gram comes from fat. Every gram of fat contains 9 calories, so depending on the serving size, a 99 percent fat-free food may contain more fat calories than you would expect.

Related: The 30 Healthiest Foods

Smart shopping tip: As a general rule, the fat content in most products that you purchase should be no more than 20 percent of the total calories, Ginn said. The exception to this would be whole foods that are naturally higher in fat, such as nuts, eggs, oils, and meats.

“Reduced Sugar,” “ Low Sugar,” or “ No Sugar Added”
Unfortunately these labels aren’t synonymous with “low calorie.” “Reduced sugar” means the product contains 25 percent less sugar than the original form. “Low sugar” isn’t a regulated term and can mean anything. “No sugar added” simply indicates that no sugar was introduced during the preparation, cooking, or baking process—not that the product is low in sugar. It may contain fructose, which still shows up as “sugar” on the nutrition-facts panel (as with unsweetened applesauce, for instance).

Smart shopping tip: Give yourself a reality check by calculating sugar content in teaspoons. First find the number of grams of sugar in one serving of the product. Four grams of sugar equal about 1 teaspoon. The American Heart Association recommends women consume a daily maximum of about 6 teaspoons (or 24 grams) of added sugar (meaning sugar that’s beyond what food naturally contains). And remember: Even if you don’t see sugar in the ingredients, it might be there.

“Sugar is the master of disguise,” Taub-Dix said. It goes by many other names, including molasses, evaporated cane juice, nectar, corn sweetener, honey, syrup, and anything ending with -ose (sucrose, dextrose, fructose, maltose). It’s all still sugar.