No. 3: Energy bars and drinks

Page through any fitness magazine and you'll begin to see a pattern in the advertising. Words like "power," "fit," "edge," "endurance" and "energy" are splayed across the rippling muscles of men and women covered in inexplicably attractive sweat beads.

The man has just finished the Ironman. The woman came in ahead of him. If you eat the same energy bar they do, you must be doing something right, the ads say.

Perhaps, if you actually require a vast amount of energy. But be especially diligent when tossing what Kostas calls "glorified candy bars" into your cart. "People think they are (healthful) because they look at the ingredients and see vitamins and minerals added," she said. "But often the first ingredient is sugar."

The first ingredient should always be a whole grain and sugar one of the last, Kostas said.

Energy drinks, too, are usually suspect: "Many times, it's just caffeine and sugar," Kostas said.

olive oil, olives

No. 2: Oils

Over the past several years, every food expert from TV chefs to the Italian grandmothers on spaghetti sauce commercials have been proclaiming the benefits of natural oils.

Olive oil has gotten the most promotion, although avocado, almond and sunflower oils are becoming increasingly easy to find.

But watch the spout -- too much any of these can add up very quickly, Kostas warned.

"Limit it to maybe 1 tablespoon for your whole dinner. Many people think the more the better, and end up getting one-fourth of a cup, adding 500 calories instead of 25 to their dinner."

When it comes to oils, even the "healthy" ones, less is definitely more. And the same goes for our last "healthy" food selection.

mixed assorted nuts closeup

No. 1: Nuts

Just as with oils, the key to keeping this seemingly innocent party food in the healthy category is moderation.

"This is definitely one case where more is not necessarily better," Kostas said. Almonds, for example, are high in vitamin E and magnesium and contain very little cholesterol.

But 1 ounce of almonds -- dry-roasted, with no salt -- contains 170 calories and 15 grams of fat. Kostas said one-quarter cup a day may be fine, or even less.

"But not a whole cup," she said. "Many people overdo nuts."

Overall, most of these foods are, in fact, healthy. But keeping them on the "good for you" list requires a bit of restraint, measuring and reading of ingredient lists, where, unlike the health section, there's no stretching the truth.