8 healthy foods that could wreck your diet

Cutting the junk from your diet is the first step to weight loss. But sometimes, the healthy foods you swap in are surprisingly high in fat and calories. That's why serving size matters—even when it comes to fruits, nuts, yogurt, and salads.

So stop sabotaging your diet, and follow our guide to healthy, but sneaky, foods. You'll also get advice on diet-friendly swaps and serving sizes, making it easier to indulge in meals that are truly guilt-free.

Health.com: Best Snacks for Weight Loss

Avocado
This superfood is packed with good-for-you nutrients and antioxidants, as well as belly-filling fiber and heart-healthy monounsaturated fats. But if your goal is to lose weight, you'll need to watch your intake. Avocados are high in fat and calorically dense. One serving size is about 1/5 of an avocado, and clocks in at 50 calories, and a single avocado can deliver more than 350 calories. This means that the small bowl of guacamole you enjoy so much is more than a snack—it's actually getting closer to a whole meal.

Get it guilt-free: Just watch your portions!

Red wine
People who consume moderate amounts of red wine (and other types of alcohol, too) may be at reduced risk for heart disease, Alzheimer's, certain types of cancers, and even weight gain. The key word: moderation. A 5-ounce serving is about 130 calories.

Get it guilt-free: Beware fishbowl-sized glasses, which make you more likely to overpour. Pour your wine into a measuring cup, and then dump it into your glass to see what a serving looks like in your glassware.

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Chocolate
Dark chocolate contains disease-fighting polyphenols and has even been associated with weight loss—if you don't eat too much of it, that is. An ounce of dark chocolate packs in 155 calories and 9 grams of fat, 5 of it saturated.

Get it guilt-free: Snack on dark chocolate that contains a high percentage of cacao—that means it's less sugary. Have just a couple squares at a time.

Nuts
Nuts are packed with heart-healthy omega-3 fatty acids, protein, vitamin E, and fiber—but they're also high in calories. A quarter-cup of almonds, for example, contains 132 calories. It's all too easy to eat them by the handful, like popcorn.

Get it guilt-free: Measure out a serving rather than eating straight from the container.

Health.com: Best and Worst Nuts for Your Health

Trail mix
Nuts, dried fruits, and oats—what could be so fattening about that? Some store-bought brands pack in ingredients like honey, added sugar, and chocolate and can set you back hundreds of calories. Plus, as you already learned, nuts are high in fat.

Get it guilt-free: Make your own trail mix and limit yourself to a quarter-cup serving.

Dried fruit
Dried fruits are just normal fruits that have had the water taken out of them. So, a cup of dried fruit packs five to eight times more calories and sugar than a cup of the fresh stuff. Here's some perspective: a cup of fresh grapes is 60 calories, while a cup of raisins is a whopping 460.

Get it guilt-free: Go for fresh fruit whenever possible. Use dried fruit sparingly as a garnish, not as a snack.

Smoothies
What could go wrong with a frosty glass of blended fruit, veggies, and ice? When they're made with ingredients like chocolate, peanut butter, frozen yogurt, or flavored syrups and served in huge cups, then they quickly become a sneaky source of added calories. Some are no healthier than a milkshake!

Get it guilt-free: To prevent your blended beverage from becoming a calorie bomb, it should contain nothing other than fresh or unsweetened frozen fruit, ice, plain yogurt, and unsweetened milk.

Health.com: 26 Healthy Smoothie Recipes

Gluten-free packaged foods
If you have a gluten intolerance, then you must drop wheat, barley, and rye from your diet to stay healthy. But gluten-free products aren't necessarily diet-friendly. Gluten-free packaged foods often replace regular flour with cornstarch and brown rice flour, which are more calorically dense.

Get it guilt-free: Whether or not you're on a gluten-free diet, you should try to eat as many whole, natural foods as possible, and limit your intake of heavily processed foods.

30 Healthy Foods That Could Wreck Your Diet originally appeared on Health.com.