This is the time of year when most people worry about their waistlines. The diet industry has become a $40 billion a year industry.

But this New Year delivers a serious warning for parents, an unintended consequence of the pre-occupation with dieting.

According to spam mail, pop ups, and magazines, the answers to obesity are found in grapefruit, cabbage and even chocolate. They are all fad diets and you’ll find an endless supply. But some are dangerous and new report released Tuesday suggests their marketing may even be worse.

Fad dieter Keli Bolling talked about her experience with the South Beach diet, "you are supposed to lose 7 pounds the first week and I did!”  

But four months later, Bolling’s success was measured. That’s true of most fad diets.

"I lost about 25 pounds in about four months. Since then, I've put about 12 back on. So that was fun but it would have been more fun if I could have maintained it," Bolling said.

Just like our dieter discovered, some fad diets work at first. And even our Carolinas Health Care expert has to agree.

"A fad diet for a short period of time is not going to kill you," said Lauren Hathcher, ”They need to begin to lose weight in a way that leads them to eating better for the long term so they can keep that weight off.”  

In fact, some diets are dangerous. They don’t have enough calories or nutrients which could actually make you sick or damage your heart. No one knows that better than Madison Tillman. She said her mother is anorexic.

"Seeing someone like my mother who eats so little. She is so thin and her skin hangs off her bones and she can't stand it and she wants to gain more muscle," Tillman said.

Madison said she grew up eating fad diets.

"I can't count them. Um, the grapefruit diet, there's the South Beach diet. There's the peanut butter diet because you can have just a little bit because it's filling," she remembered.

Madison is only 16-years-old and is part of a group of girls that researchers are especially concerned about. A new study shows that girls exposed to articles about dieting are more susceptible to eating disorders and extreme dieting five years down the road. Madison’s already seen that at her school, “people have just gone on water at my high school like they would go two weeks without eating."

Our expert said if you want to lose weight immediately and safely, start with soda. It’s full of sugar and high in calories. You’ll also get a little support from Starbucks this week; they are going trans fat free this week.