Most people think of fruit as a calorie freebie, but it's not. Most eat fruit without considering portion size, and they should not.

"One medium pear has about a hundred calories, more than most medium cookies, so that's something you really have to keep in mind,” says Pam O'Brien, deputy editor at Shape Magazine.

Fruit is not something you should add on top of everything you already eat. It should replace something already in your diet.

"If you're having pancakes, don't just have a side of fruit. Put the fruit on top of your pancakes and don't have syrup, and that way you'll actually reduce the number of calories you're eating,” O'Brien says.

Fructose is natural sugar in fruit, but still if you eat too much of it, the sugar grams really add up.

"Some of the sweetest fruits have less sugar in them, which you wouldn't think. Like strawberries, super sweet, but they only have seven grams of sugar,” O'Brien explains. “Watermelon has just nine grams of sugar, but grapes have 23. You can look at fruits and the sugar they contain and try to figure out which are going to give you the most bang for your buck."

You have to be careful, especially if you're drinking a lot of fruit juices.

"It hits your bloodstream a lot faster because it's a liquid and so your blood sugar spikes and you get an energy high, but then a crash," O'Brien says.

And just because fruit has fiber doesn't mean it will give you that full feeling.

"Fiber is great but you also need protein and fat,” O'Brien explains. “So if you eat an apple, you know, have some peanut butter with it or have some cheese with it, that way you're getting enough protein and fat to help keep you feeling satisfied because you need those nutrients as well."

She says if you have a healthy diet, you should stick to two servings of fruit a day. If you are trying to lose weight, you should reduce it to one. And remember, a serving size is a half cup of chopped fruit or one medium-sized piece of fruit.