It's been said that the best things in life are free. Many people think when they see low-fat or fat-free foods that they've hit the jackpot. They can eat as much as they want because the item contains little to no fat.

Associating "reduced fat" or "low fat" with fewer calories is an easy trap to fall into, especially when you have a sweet tooth to please. You bought the low-fat version of your favorite chips, so you should get to eat an extra handful or two, right? Probably not.

Unfortunately, foods labeled fat-free, reduced fat, low-fat or sugar-free don't equate with calorie-free — and they often contain additives like salt, sugar and chemical fillers that make them less-than healthy.

Rather than trusting health claims on the front of the package, it may be worth checking the nutrition facts — and learning which fats to look for.

Make the nutrition label your source of truth

It may add more time to your shopping trip, but you'll need to take a critical eye to the nutrition label if you want to choose a healthy snack. Not only does it tell you calories per serving, it also shows the serving size — which manufacturers often set to be unrealistically small.

Kari Kooi, dietitian at Houston Methodist, says reduced-fat products often contain almost the same number of calories per serving as full-fat versions.

Plus, reduced-fat foods have a perceived healthy image, and studies have shown that people tend to eat twice as much or more of these foods.

It's also important to know that fat-containing foods aren't actually bad for you. In fact, Kooi says that fats play a strong role in feeling satisfied after eating, therefore helping with appetite control, and should make up at least 30% of your daily calories.

Turn to healthy fats instead

Instead of looking for products with health claims such a "low fat," Kooi suggests concentrating on eating fats that are healthy for you.

Monounsaturated fats found in whole foods such as nuts, olive oil and avocados have been shown to lower LDL (bad) cholesterol and boost HDL (good) cholesterol in the blood. Moreover, omega-3 fats in oily fish such as salmon and anchovies have been shown to lower LDL.

Kooi also recommends avoiding trans fats as much as possible, as this type of fat promotes inflammation in the body. Products that contain partially hydrogenated oil in the ingredients list have trans fat.

The best way for all of us to avoid being fooled by low-fat labels — and putting on those unwanted pounds — is to shop for nutrient-dense foods that don't come in a package and therefore require no labeling.