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7 Common Diet Foods Making You Gain Weight

If you're eating "diet foods," but you're still gaining weight, it may be worth reassessing whether those foods are helping or hurting.

Reality and our perceptions of the truth are often two very different things, whether that's with someone you meet on a dating website or a protein bar. Our wide sphere of influence creates our own brand of reality.

Research related to the healthfulness of food products suggests that we are influenced this way, too. Specifically, it's called the "health halo effect." It describes our preconceived notion that an item labeled low in calories or low in fat is better for us. One poll of consumers published in Plos One found that 40% of consumers eat more of a food bearing a healthy label because they believe the claim.

If you think you are eating "diet foods" and still gaining weight, you could be confused by product labeling and eating too much of something you should be overeating. Here are some foods that are commonly thought of as "diet food," that could secretly be making you gain weight. Read on, and for more on how to eat healthy, make sure you avoid these 100 Unhealthiest Foods on the Planet.

Low-Fat Yogurt

fat-free yogurt

Here's a classic example of health halo food. "Low-fat" and "fat-free" yogurt may sound healthy, but the missing fats are often replaced by lots of added sugars. For example, a 2/3 cup serving of Yoplait Original Strawberry Banana Low-Fat Yogurt contains 150 calories and 22 grams of sugar, of which 17 are added sugars. Don't automatically fear fat when it comes to weight loss. A 2016 study in The American Journal of Clinical Nutrition followed a large group of women for 100 years and found that those who included more full-fat dairy products in their diets gained less eight than low-fat dairy eaters.

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Bottled Fat-Free Salad Dressing

salad dressings in jars

What can be healthier than salad greens topped loaded with chopped fresh vegetables? Such a salad that isn't drenched in bottled fat-free dressing. For one, some of the powerful antioxidants, such as carotenoids, in those veggies are fat soluble, meaning they need to be eaten with some fat to be absorbed by your body. That fat-free dressing won't do you any good. What's more, while you won't find fats on the ingredients labels of fat-free dressings, you will find sugar. High fructose corn syrup is often the second most abundant ingredient after water. You'll find 3 or 4 grams worth per 2 tablespoon serving. But are you using just 2 tablespoons? Don't bet on it. (Related: 20 Unhealthiest Salad Dressings on the Planet—Ranked!)

Diet Soda


Reducing added sugars in your diet by choosing a no-calorie soft drink over a 150-calorie soda may sound like a good idea. It may even help you lose weight. On the flip side, it may make you gain weight. How so? Well, some people rationalize consuming more food calories when they wash down their meals with diet drinks. And that can backfire. University of Texas Health Science Center monitored 475 adults for 10 years and found that the participants who drank diet soda saw a 70 percent increase in waist circumference compared to those who didn't drink soda.

Researchers believe that artificial sweeteners like aspartame, saccharin, or Splenda may play a role. Because these super-sweet chemicals don't come with the calories their sweetness suggests, our bodies may end up craving foods that are much more sweet than typical nutritious foods, suggests the Harvard Medical School's Harvard Health Blog. In addition, a review of studies in the Yale Journal of Biology and Medicine suggests that because they are so sweet, "artificial sugars encourage sugar cravings and sugar dependence." When you eliminate the calories from sweet beverages, you reduce the reward of satisfaction from those calories, "which further fuels food-seeking activity…and may contribute to obesity," writes study author Quing Yang of Yale's Department of Molecular, Cellular and Developmental Biology. Do you have these Warning Signs You're Drinking Too Much Coke?

Light Wheat Bread

whole wheat bread

Don't be fooled by the "wheat" on the label of your loaf of bread—it's not as well-meaning as it seems. What "wheat" means, actually, is simply that your bread is made from wheat flour. Now, manufacturers are taking this health halo a step further by inserting this healthy-sounding word into their typical list of ingredients. White wheat bread? It's the same as white bread. And both mean that the wheat grain has been stripped of fiber. Look for "whole wheat" or "whole grain" flours on the ingredients label to ensure you're actually getting a whole wheat bread. Secondly, the term "light" refers to a bread that's lower in calories because it has been stripped of its nutrients, including fats, and replaced with added sweeteners, often high fructose corn syrup. You're better off swallowing more calories with a whole grain bread that contains more vitamins, fiber, and other nutrients. To help you identify these diet saboteurs, don't miss these The 18 Unhealthiest Breads on the Planet.

Convenience Store Yogurt Parfaits

Yogurt parfait

You run into a convenience store for a quick hunger buster but want something healthy. Then you spot it—the store-made yogurt parfait with layers of sliced strawberries and granola. You skip the Snickers bar thinking you've made a smart choice, when you're swallowing the same number of calories 280 and grams of sugar, 28. If you want your yogurt to really be a diet food, you'll want to try any of these 25 Best Yogurts for Weight Loss, According to Nutritionists.

Energy and Protein Bars

nut and seed energy bars

With so much hype about the weight-loss benefits of protein, we've lost sight of the fact that high-protein packaged foods still contain lots of calories and maybe even added sugars. Energy and protein bars are a prime example of convenience store snacks wearing health halos. Their packaging signals healthy fuel, but the nutrition facts tell a different story. Many are loaded with sugars and calories. Take two of the most popular for example, CLIF's Chocolate Chip Energy Bar packs 21 grams of sugars and 250 calories; PowerBar Performance Peanut Butter Energy Bar contains 26 grams of sugars and 230 calories. Check out our rankings of the best and worst energy bars.


Popcorn bowl

The air-popped kind unadulterated with oils or butter is a healthy snack for weight loss; it even contains fiber. But don't think all popcorn is good-for-you popcorn. "Movie theater popcorn is like chowing down on a stick of melted butter or drinking salted oil," says Ilana Muhlstein, RD, author of You Can Drop It! How I Lose 100 Pounds Enjoying Carbs, Cocktails & Chocolate—and You Can Too! Microwave popcorns containing "butter flavoring or "caramel flavor" can include up to 6 grams of saturated oils per serving (30% of your daily value), so be sure to read nutrition and ingredient labels. Or, just read our guide: 9 Healthiest Microwave Popcorn Brands (& The Bags to Skip).

Jeff Csatari
Jeff Csatari, a contributing writer for Eat This, Not That!, is responsible for editing Galvanized Media books and magazines and for advising journalism students through the Zinczenko New Media Center at Moravian University in Bethlehem, PA. Read more about Jeff
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