"Just like with any way of eating, you still need to be concerned with certain issues," she said. "Even if it is a vegetarian diet, it does not necessarily mean it is a healthy diet."
Specifically, vegetarians must find sources other than meat for protein. Those who opt to go vegan must be even more vigilant when it comes to finding substitutes for other nutrients, such as the calcium that they might otherwise get from dairy products.
But with unhealthy eating behaviors, restrictive eating goes even a step further. If teens are motivated more by weight than by health, they may end up cutting back their calories to dangerous levels -- or bingeing and purging.
Barnard contended, though, that the fact that the study was based on self-report -- that is, answers that the young subjects provided themselves -- suggests that perhaps some of these kids did not understand what it meant to be vegetarian.
Indeed, researchers in the study found that among those who identified themselves as vegetarian, 46 percent said they still ate fish and more than 25 percent said they ate chicken. In this light, he said, it was more likely that some teens simply used vegetarianism as a cover for their unhealthy eating habits.
With this in mind, parental involvement in teens' diets may be even more important than parents realize.
"Parents should try to help their teens," Gans said. "The best thing that parents can do is work with their teens to help them create a healthy meal plan. If they are confused, they should consult a dietitian."
Barnard said that parents should make an effort to spend time with their teens at mealtime to ensure that they are eating a healthy diet.
"When parents eat with their children, that helps -- they actually can see what their children are eating," he said. "If they are with them after the meal, as well, they are going to know if they duck out and vomit."
"Having said that, kids can hide these things."
Waller noted that it may even be a good idea to get doctors involved -- particularly if parents are concerned that their child may indeed be hiding an eating disorder behind a vegetarian label.
"It is important to have some ongoing meetings at the pediatrician's office just to see that this person is not losing control of normal eating behaviors," he said.