It may make you scratch your head, but in fact it is possible to overeat healthy foods, according to Loyola University Health System registered dietitian Brooke Schantz.

"While fruits are nutritious, too much of even a healthy food can lead to weight gain," Schantz said. "The key is to remember to control the portion sizes of the foods you consume."

Schantz reported that overeating healthy foods is easy to do, but the same rules apply to healthy food as junk food. Weight fluctuates based on a basic concept -- energy in versus energy out. If your total caloric intake is higher than the energy you burn off in a day, you will gain weight. If it is lower, you will lose weight.

"I have had many patients tell me that they don't know why they are not losing weight," Schantz said. "Then they report that they eat fruit all day long. They are almost always shocked when I advise them to watch the quantity of food they eat even if it is healthy."

Schantz said that one exception applies. Nonstarchy vegetables are difficult to overeat unless they are accompanied by unnecessary calories from sauces, cheeses and butter. This is due to the high water and fiber content of these vegetables coupled with the stretching capacity of the stomach. The vegetables she suggested limiting are those that are high in starch, such as peas, corn and potatoes. Foods that are labeled as fat-free or low-fat are another area of concern.

"People tend to give themselves the freedom to overeat 'healthy' foods," Schantz said. "While the label might say that a food or beverage is low-fat or fat-free, watch the quantity you consume and refrain from eating an excessive amount. Foods that carry these health claims may be high in sugar and calories."