Pay attention to these food labels that sound healthy but aren't.

More and more "healthy" buzzwords are appearing on food packages. But proceed with caution. Just because a product lacks fat, gluten or sugar doesn't mean it's healthier-some labels are flat-out confusing. Here are some labels frequently found on packages and what they really mean:

-Patricia Bannan, M.S., R.D. & Katie Andrews and EatingWell editors


1. Fat-Free

You might think you're making a healthy choice, but eating certain fat-free foods may cause you to gain, not lose weight. In a new study from Purdue University, rats fed potato chips containing Olean (a no-calorie, fat-free fat substitute) subsequently put on more weight than rats fed regular chips. More research is needed, but experts think fat substitutes may interfere with your body's natural ability to regulate how much food is enough, causing you to eat more.


2. Gluten-Free

If you don't have celiac disease or gluten sensitivity, think twice before ditching gluten: being gluten-free doesn't automatically make a product better for you. Gluten-free products can vary greatly in the amount of fat, protein and other nutrients they contain. Some gluten-free breads have up to 13 times more fat and 16 times more protein than others, according to a recent study that compared 11 different gluten-free breads.

Diet Soda

3. Diet Soda

To most, the word "diet" equals weight loss. But diet soda may not be holding up its end of the bargain. Researchers at the University of Texas Health Science Center at San Antonio recently found that people who drank two or more diet sodas daily had a six-times-greater increase in waist circumference at the end of the 10-year study than those who didn't drink diet soda at all. Those bigger waist sizes may be due to the "I saved here, I can splurge there" theory of dieting, says researcher Sharon Fowler, M.P.H. Or perhaps the artificial sweeteners in diet soda stoked diet-soda drinkers' appetites, as other research suggests.


4. Organic

People asked to rate "organic" versus "conventional" yogurt, cookies and potato chips overwhelmingly said they preferred the taste of the organic ones-and thought they were healthier and worth a higher price tag, according to a new Cornell study. The catch? All products in the study were actually identical, just labeled differently.

Trans-Fat Free

5. Trans-Fat Free

Since 2006, the FDA has required food manufacturers to list reportable amounts of trans fat on the Nutrition Facts label. But here's the thing: food manufacturers don't have to report the trans-fat content if it's less than 0.5 gram per serving. So check the ingredients list for the terms "hydrogenated" or "partially hydrogenated vegetable oils" even if the Nutrition Facts label reports 0 grams of trans fat.