Marketing wizards at food industry giants love to use labeling to entice you to pick up their product over competitors, and over fresh produce. They’ll emblazon their packaging with flashy clarion calls like “No Fat!” or “Low Sugar!” to tempt you to toss it into your cart—and pre-empt any scrutinizing of the boring nutrition facts label on the back of the box.

But as you may have suspected, those front-of-box labels could just be a false sense of security, according to a recent study out of the University of North Carolina at Chapel Hill. Researchers pored over more than 80 million food and beverage buys from over 40,000 households, spanning 2008–2012, and discovered that 13% of the food bought had a low-content claim—like low calorie, low fat, no sugar—and 35% of the drinks did.

The real kicker? “In many cases, foods containing low-sugar, low-fat or low-salt claims had a worse nutritional profile than those without claims,” said study author Lindsey Smith Taillie, Ph.D., a research assistant professor in the department of nutrition at UNC’s Gillings School of Global Public Health. “In fact, in some cases, products that tend to be high in calories, sodium, sugar or fat may be more likely to have low- or no-content claims.”

For example: A low-fat brownie may have 3 grams of fat per a 40g serving, while a low-fat cheesecake would have 3 grams of fat per a 125g serving. “So if a consumer were trying to find a lower-fat option for a dessert, the low-fat brownie would have relatively higher fat than the low-fat cheesecake," even though they may look about equal on the nutrition facts label.

This confusion all comes from the fact that the FDA lets companies make those low content claims if the reduced amount is lower compared to the original food product for that particular nutrient. Since the claim is relative and only about one ingredient, it creates the illusion that you're buying something healthy.

Our advice? Just limit your packaged food to the bare minimum and don’t even look at any labels except the nutrition facts and ingredient lists, and you’re bound to eat healthier in the long run.