Ever wonder why you can’t lose weight even though you’re eating “healthy?”

More than likely it’s because you’re misinformed as to what really constitutes healthy food, nutritionist and dietician Tanya Zuckerbrot told Foxnews.com.

“When I see some of the food choices people make I wonder if it’s just that people don’t care,” said Zuckerbrot, author of the F-Factor Diet. “But I really think it’s just that people don’t know what’s good for them and what’s not.”

Here are 10 healthy foods that aren’t:

Olive oil: Sure it’s a heart-healthy monounsaturated oil, but it’s also rich in calories and fat. “Oil is oil,” Zuckerbrot said.

“Whether it’s olive oil or some other kind of oil, it still has 120 calories and 14 grams of fat per tablespoon. You’re better off using a pat of butter (for bread) than dipping it in olive oil because the bread sops up the oil like a sponge. So a little bit of butter is better than a lot of olive oil.”

Tuna fish: Think that tuna sandwich is a light lunch? Think again. The average overstuffed tuna sandwich served in a restaurant contains 700 calories and 43 grams of fat.

The reason? The mayo. “Tuna fish has just 35 calories per ounce and it’s full of omega-3s, but mayonnaise has 100 calories per tablespoon,” Zuckerbrot said. “You’re better off having a turkey or even a roast beef sandwich. Even chicken salad is better than tuna salad, because tuna is so fine there’s a lot more surface area for the mayonnaise to fill.”

Granola: The term granola may be used to describe health-conscious people, but the cereal itself is actually quite fattening. That’s because granola cereals often contain oils, including high in saturated fat coconut oil, sugar, nuts and other high calorie foods.

“Something like Fiber One has 60 calories per half cup and 14 grams of fiber versus a half cup of granola, which was 240 calories, 5 to 10 grams of fat and just 3 grams of fiber,” Zuckerbrot said, adding that fiber is the key to feeling full and satiated.

Organic food: Organic food may be preservative and pesticide free, but that doesn’t mean it’s also calorie-free, said Zuckerbrot. “I mean they make organic potato chips so what does that tell you,” she said.

Sushi: Tuna sashimi is very healthy. A California roll or tempura roll, not so much, said Zuckerbrot.

“Japanese food is inherently healthy, but when you Americanize it and start adding things like cream cheese and avocado, that’s when you run into problems,” she said.

Tuna sashimi, for example, has about 35 calories and 1 gram of fat per ounce. But a spicy tuna roll has 290 calories and 11 grams of fat, and a tempura roll has 320 calories and 17 grams of fat. “You’re better off going with tuna sashimi, miso soup (36 calories) and a salad (35 calories with a tablespoon of non-creamy ginger dressing).”

Pizza: “Yes the sauce is high in lycopene, but all the lycopene in the world is not going to convince me pizza is a heart-healthy food,” Zuckerbrot said. “And mozzarella cheese is a good source of calcium, but it’s also high in calories.”

An average slice of pizza sold in New York City has between 600 and 700 calories. A more traditional slice, about one-twelfth of a pie, has between 300 and 400 calories, said Zuckerbrot. “And most people eat at least two slices to feel satisfied,” she said. “Your best bet is to eat one slice and get a salad or a cup of minestrone soup on the side so that you feel satisfied and save on the calories.”

Frozen diet meals: Sure Lean Cuisine and Weight Watcher frozen entrees are fairly low in calories and convenient, but they’re also highly processed and high in sodium.

“I understand the convenience factor, but most of these meals have more than 600 milligrams of sodium and the portions are really small and they’re not really satisfying,” Zuckerbrot said. “So you eat one for dinner and then by 9:00 you’re hungry again. You’re better off eating a slice of whole wheat bread with some light sauce and light mozzarella or an egg white omelet with some vegetables.”

Protein bars: Another convenient food, but not very nutritious. Zuckerbrot describes protein bars as her least favorite food and said they are basically glorified candy bars. They’re also often high in calories, fat and do little to satisfy a person’s hunger.

A better choice, said Zuckerbrot, is hitting the salad bar and grabbing lots of lettuce, artichokes and broccoli, topped with plain balsamic vinegar. For 100 to 200 calories, you get a lot more for a lot less calories.

Pretzels: They’re low in fat and low on nutrition. “They’re basically empty calories,” Zuckerbrot said. “Inherently, pretzels themselves are not unhealthy, but they’re basically all sugar so they’ll make you hungrier and you’ll gain weight as a result of over-eating."

Fat-free, sugar-free muffins: Regardless of whether a muffin is fat free or sugar free, they still usually have around 600 calories, according to Zuckerbrot.

“It’s nothing but cake in disguise, especially these double chocolate chip-type muffins,” she said. “But even bran muffins, they’re very dense, very high in calories. The same thing goes for scones. People think that because they’re not sweet, they’re healthy. But scones are full of butter.”