On the surface, it would make logical sense to assume that those who weigh more consume more calories than their normal weight counterparts, but as with many things, teenagers can be very surprising.

In an effort to determine the ideal amount of calories obese teens should eat to help them lose weight, researchers recently analyzed statistics on almost 20,000 children ages 1 to 17 who took part in the decade-long National Health and Nutrition Examination Surveys.

At first glance, the researchers found that about 3 percent of the children were underweight, while about 66 percent were at a normal healthy weight. Fifteen percent were overweight, and 16 percent were considered to be obese or very obese.

As expected, the investigators found that among younger kids, the obese and overweight children took in more calories than those harboring a healthy weight. But surprisingly, the results were very different for older children.

Among obese boys over 12 and girls over 9, the number of calories they consumed was actually lower than for those considered to be at a healthy weight … and the difference was significant. In essence, the obese were eating less, but still maintaining their extra weight.

The researchers noted that the study, recently published in Pediatrics, only revealed the trend and not necessarily the reasons why. But they hypothesized that once children overeat at a young age, the less calories they need to maintain that obesity as they get older. And more than likely those children are getting less exercise too, which means more added weight.

Best advice? Researchers encourage parents to be aware of a child’s weight early on. Promoting exercise and healthy eating should help keep the extra pounds from adding up.