Frozen yogurt
You really have to read the label. While some brands are relatively low-calorie, others have even more calories than light ice cream and, thanks to added sugar, some premium brands pack up to 185 calories per half-cup.

Vegetarian doesn't necessarily mean that what you're eating is healthy. Falafels are chickpea-and-herb balls fried and covered in creamy dressing, which means that a falafel pita can contain up to 550 calories and 32 grams of fat.

Fat-free snacks
Most of these snacks have almost no fiber and are easy to eat in huge quantities because they're not satisfying. Many have even more calories per serving than the regular version in order to compensate for the lack of taste, so you could end up consuming a lot more calories than if you just ate a reasonable portion of the high-fat food you were craving in the first place.

Skip the popcorn at the movies. The smallest bag, without the extra butter, packs up to 300 calories and 20 grams of fat. The microwave kind can be even worse; many brands have almost 400 calories and 26 fat grams per bag. Choose air-pop or a reduced-fat microwave version. Try seasoning with garlic chili powder.

Olive oil
With less than two grams of saturated fat per tablespoon, olive oil is healthier than most vegetable oils and it may even reduce your risk of heart disease. However, keep in mind that it's still oil; one tablespoon contains 120 calories and 14 grams of fat.

Frozen diet meals
They may be convenient, nutritious and low in fat and calories, but most are full of sodium, which can raise both your blood pressure and risk of heart attack.

Protein bars
These were designed for hard-core athletes. Although they're not bad for you, they can contain up to 300 calories and more protein than you need in an entire day.

Fast-food grilled chicken
Although grilled is definitely better than fried, most fast-food grilled chicken sandwiches are full of fat due to all the cheese and creamy toppings they're smothered in. Burger King's BK Broiler chicken sandwich, for example, contains 530 calories and 26 fat grams.

Granola bars
Most granola bars contain lots of hydrogenated oil, which means that two-thirds of a cup adds up to about 380 calories and 20 grams of fat.

Tuna salad sandwich
The tuna itself is very healthy; besides the fact that it is low in calories and fat, it is a great source of protein and healthy omega-3 fatty acids. The problem is all the mayo that usually goes into it. A typical restaurant tuna sandwich contains up to 720 calories and 43 grams of fat.

Most muffins are nothing but cake in disguise. Even bran muffins, which don’t usually contain much bran, will bust your diet with up to 600 calories and 25 grams of fat. Fat-free muffins often contain lots of sugar to compensate.

The culprit in most salads is the dressing. In fact, if your salad is drowned in creamy ranch or blue cheese dressing, you could be getting as many calories as you would with a huge plate of fries. Not surprisingly, the most popular salad in the U.S., Chicken Caesar, is also the most fattening. According to the Center for Science in the Public Interest, a typical chicken Caesar salad contains 660 calories and 46 grams of fat.