HOUSTON -- Low-carbohydrate diets are the latest rage in losing weight. It seems more and more people are dropping pounds on the Atkins and South Beach diets.

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But these weight-loss plans can be dangerous for kids. Carbohydrates are needed for healthy bodies and brains, according to dieticians.

"Carbohydrates is the body's preferred source of fuel, so for an active child, that's a problem," said Jennifer Thomas, a dietician with Texas Children's Hospital in Houston.

As the senior clinical dietician at the hospital, Thomas treats a lot of overweight children. But she said low-carb, high-protein diets are not the way to solve the problem.

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"Some of the low-carb diets eliminate things that we know have known health benefits, so I have some concerns with that," Thomas said.

Thomas is talking about plans that limit or eliminate whole grains, fruits and vegetables.

Registered dietician Catherine Kruppa said that children need carbohydrates to think.

"Carbohydrates are the only fuel for your brain," Kruppa said.

Teenager Natalie Garza decided she needed help with her eating habits since she was overweight.

"At school, I would usually eat French fries or a bag of chips and a Coke, and stuff like that," Garza said.

Garza, who wore women's size 14 pants, had to alter her dance team uniform so fabric could be added.

"We were all excited to get our dance costumes and they looked great on everybody else but me," she said.

She went to Texas Children's, where a dietician showed her how to eat and exercise properly without fad diets. She has lost 26 pounds in less than six months.

"I'm very happy now because I can shop at all the stores that my friends shop at. I can wear the new cool clothes that everybody else is wearing," Garza said.

She said her new eating habits are easy -- three meals a day and one snack.

"That way, your metabolism is always running," she said.

Garza also limits portion sizes.

"I can eat everything. I just have to watch the portion size. You should be able to fit it in the palm of your hand," she said.

Exercise is also important.

"I have to do my crunches, my push ups," Garza said. "This is the healthy way to lose weight."

Dieticians said a lot of people on a low-carb plan eat lean meats and a lot of vegetables. They said that if people had done that in the first place, they would not need to go on a low-carb diet.