We all know that certain foods have more calories than others. It’s pretty obvious: if it’s covered in a sheen of oil, it’s most likely full of calories. But certain foods might not appear to be as caloric as they are, and the main culprit is serving size.

Two major culprits when it comes to packing in the calories are sugar and oil. The sweeter or greasier a food is, the higher the calorie count. And it doesn’t take much to tip the scales: a tablespoon of canola oil contains 124 calories, and the same amount of sugar (about 12 grams) contains 45 calories. Those are quantities that are acceptable by most people’s definitions, but the amount of sugar that goes into one smoothie, for example, can be jaw-dropping.

It’s good to keep in mind that unless you’re on a super-strict diet, a little bit of just about anything is okay. But there a lot of foods out there that we eat much more of than we should in one sitting, and the calories can really add up.

Even a small amount of these foods can contain more calories than you think, so use discretion. Several of these have a reputation for being healthy as well, but that’s not always the case once you exceed the serving size portion. So while we’re not saying that these foods are unhealthy by default, they simply contain more calories than you probably realize. The best way to avoid going overboard? Stick to the serving size, and if you’re dining out, watch the portion size.

Salad Dressing
A tablespoon of ranch dressing contains 145 calories. But measure out a tablespoon and try to mix it into an average-sized salad and you’ll most likely be left with a lot of plain lettuce. The average salad can contain up to 5 tablespoons of dressing, which can add an additional 725 calories to your diet. Stick with vinegar, salt and pepper, and a measured tablespoon of extra virgin olive oil.

Fried Chicken/Chicken Fingers
Another no-brainer here, as any time something is breaded and fried (even if it’s white-meat chicken) there’s going to be a lot more calories than you might expect. For example, one KFC Original Recipe breast contains 320 calories, but who stops with just that? And remember that time you ordered the chicken tenders platter at Applebee’s? We hate to break it to you, but that contains 1,420 calories. Eek!

Chicken Skin
Chicken breast is one of the healthiest, leanest proteins you’ll find, but a lot of people don’t give second thought to eating it skin-on. You might want to peel it off next time, though: The average four-ounce skinless chicken breast contains about 100 calories, but if you leave the skin on it will add 100 more, not to mention about 10 grams of fat, a third of which is saturated.

Movie Theater Popcorn
If you’re used to working your way through a large popcorn over the course of a movie, you might want to reconsider. Movie theater popcorn is insanely unhealthy, with a medium popcorn from Regal clocking in at 720 calories, and a large at a whopping 960. It’s best to skip this junk all together, but if you must, get a small, and please skip that gross ‘butter’ sludge!

Subway Sandwiches
Subway’s main advertising message since the 1990s has been all about how healthy it is, and while if you stick to turkey and vegetables with no cheese or condiments on a 6-inch sub it can certainly be a part of a well-balanced diet, but most of their sandwiches contain just as many calories as their burger-chain counterparts. There are plenty of unhealthy options, however, like the Turkey Jalapeno Melt, which contains 860 calories in a footlong, and the Chicken and Bacon Ranch Melt, which at 1,140 calories for a footlong is their most calorific option.

Granola is the quintessential ‘health food,’ but it’s certainly not calorie-free. For example, there’s 140 calories in just ¼ cup of Bear Naked’s Fruit & Nut granola, which is basically a small handful. A cereal bowl’s worth usually contains a cup or more, which can push you well beyond the 500-calorie mark.

Every kid’s favorite spread is, unfortunately, the caloric equivalent of eating a candy bar sandwich. Two tablespoons of the chocolate hazelnut spread, which is enough to modestly coat a slice of toast, contains 200 calories, 12 grams of fat, and 21 grams of sugar. Compare that to a Snickers bar, which contains 250 calories, 12 grams of fat, and 27 grams of sugar, and you can see why the company’s playing up of its health benefits incensed so many people that the company was sued for false advertising.

Jamba Juice
Smoothies are still regarded as a generally healthy treat, full of fruit and other generally healthy stuff. But from a purely caloric standpoint, they’re off-the-charts: a small Strawberry Surf Rider smoother contains a whopping 320 calories, a large 590, and most small smoothies average 260 calories. Should you decide to go for a small Peanut Butter Moo’d Smoothie, that’ll set you back 480 calories.

It’s common knowledge that cheese is unhealthy, but the extent of its calorie overload might surprise you. For example, take a standard one-ounce slice of American cheese, which contains around 100 calories, and compare it to the amount of cheese you find on an average slice of New York-style pizza. Each pizza slice can easily contain four ounces of cheese, packing in 400 calories. And when you’re at a cocktail party and the cheese plate is out – the one with the little cubes of cheese – each of those cheese cubes contains about 100 calories. The fact that it’s easy to eat 10 of those without even thinking is a little bit scary.

Hope this helps!