Most people believe that to eat healthy and eat out, all you have to do is know the "right" way to order. However, we've learned secrets from restaurant insiders that will shock even the savviest restaurant-goers who think they're ordering healthy.

YOU'VE BEEN GRILLED

According to food-safety expert Jeff Nelken, when we order foods "grilled," most of us assume they'll be cooked on an open flame, but many times it's a flat-top grill, where some type of grease or oil is necessary to create an even cooking surface, increase the cooking speed and prevent the food from sticking.

Health pro: Ask if it's a flat-top grill or a flame grill. If it's flat-top, request your food be grilled in a pan with cooking spray.

OIL SLICK

There is oil on almost everything, and while some oils (e.g., canola, olive) are healthier than others, they all have about 120 calories per tablespoon. So while you may order an egg-white omelet, believing you're making a "low-calorie" choice, it could be doused in oil. Or you might order grilled or steamed vegetables — that have been marinating in oil all day.

Because fat and oil help preserve cooked food, busy restaurants usually partially cook poultry and fish and then coat it in butter or oil until it's ready to be finished, says Billy Strynkowski, executive chef of Cooking Light magazine. "Even if you order your chicken 'dry' with the sauce on the side, poultry is always pan-fried in oil or clarified butter," he says.

Pasta, potatoes and rice, again, are often partially cooked and filmed with some type of fat so that they stay fresh and don't clump together, says Juventino Avila, chef instructor at the Institute of Culinary Education in New York City.

Even if something is not doused in oil, you still may not be calorie-safe — it can have added butter or cream. Toasted buns are often covered in butter; even steaks have butter drizzled on them before they're sent out. "And restaurants always finish sauces with butter or cream — even if the words 'butter' or 'cream' are not in the sauce's name," Strynkowski says.

Health pro: Almost all the chefs agree — if you want your food cooked a certain way, tell the server you have an allergy (to whatever you want eliminated) or medical issue. This encourages the chef to make up a new batch of veggies, chicken, etc., without the added calories.

PUREE FANTASY

Most pureed soups, potatoes and vegetables are full of cream and/or butter to make them smooth and tasty, says John Greely, chef at 21 Club in New York. Some restaurants do make thick soups without butter or cream. But if that's the case, your server will almost always make a point of telling you.

Health pro: Ask about the ingredients and the preparation method, specifically if the dish has any cream, and, if not, what was used instead. Healthy, low-calorie thickening agents include pureed potatoes, roasted garlic and arrowroot. If there is no thickening agent, well, they probably used butter or cream.

SODIUM SURPRISE

Many restaurants go heavy on the seasoning, including sodium, warns food-safety expert Nelken. Most places put salt on almost everything, especially marinades. Some chicken producers even inject chickens with a sodium solution to add flavor.

Health pro: Ask for no added salt or sodium, and ask if your dish has been marinated, and if so, in what.

ALLERGIES

Almost 11 million Americans have allergies to foods such as peanuts, fish, milk and wheat, and even if your food is not made with the offending ingredient, it still may not be allergen-free. Cooks, food handlers, utensils — almost anything can infect an allergic individual, warns Nelken.

Health pro: Call ahead. If you believe something contains or has been contaminated with the allergen, avoid it.

SALAD SURPRISE

According to chef Greely, any pre-tossed salad (particularly those made in large batches) could have up to a quarter-cup of dressing when a tablespoon usually suffices.

Health pro: Order a simple "vinaigrette" dressing made with olive oil and an acid such as lemon juice or grapefruit juice, and get it on the side.

WHOLE-GRAIN MYSTERY

When we see wheat-crust pizza, whole-wheat pasta or wheat buns on a menu, most of us automatically think "healthy." But according to Marjorie K. Livingston, a professor at the Culinary Institute of America in New York, there's no real way to be sure that you're getting a whole-grain product. In fact, most of the time you're getting products that just have brown coloring, maybe with some whole-grain flour.

Health pro: Ask if it's a 100 percent whole-grain product, and if he or she is not 100 percent sure, it's probably not.

IT MUST BE TRUE

There is no law requiring restaurants to provide nutrition information for the foods they serve and many of the claims they make.

Health pro: Restaurants are required to provide information if they make a nutrition (e.g., low-sodium, low-fat, etc.) or health claim about the relationship between a nutrient or food and a disease or health condition (e.g., "heart healthy").

Charles Stuart Platkin is a nutrition and public-health advocate. Write to info@thedietdetective.com.