Half-Baked Cookie: Weight Destroyer

It sounds like a dieter's food fantasy come true: eat cookies all day long and watch the pounds melt off.

But while Dr. Siegal's Cookie Diet may result in quick weight loss, it's nutritionally unsound and can even result in weight gain, experts say.

The 1,000-calorie a day regimen, which celebs like Jennifer Hudson, Denise Richards and Kelly Clarkson have reportedly tried, according to ABC News.com, is scarily low in fresh produce, nutritionists say.

Cookie Diet followers drink water and eat six specially developed 90-calorie cookies a day, followed by a 500-calorie dinner of lean protein and vegetables. Many report great success.

Josie Raper told "Good Morning America" that she went from a size 24 to a size 6 in six months, following his plan.

"When I started the Cookie Diet, there was no splurging or sneaking little snacks," the Phoenix woman told "Good Morning America."

I was very strict and, to make sure that I could stay on the diet, I started the Monday of Thanksgiving so I got through every single holiday without snacking or caving in to my cravings."

Raper has reportedly been on the Cookie Diet for two years, and hasn't regained the weight.

(She's a size zero and doesn't need her fat pants, she told ABC News.com.).

Weight loss experts say the Cookie Diet's basic flaw is that it does not help dieters to retrain their eating habits.

"If you lose weight through diet and exercise alone and don't change anything else in your life, you are probably going to gain the weight back," says registered dietitian Anne Fletcher, author of "Thin for Life" and "Weight Loss Confidential."

"When you don't deal with the underlying reasons for why you're overeating, you're definitely more likely to gain weight."

The diet also worries Dr. Louis Aronne, director of the Comprehensive Weight Control Program at New York-Presbyterian/Weill Cornell Medical Center, because it lacks good nutrition, according to ABCNews.com.

"I am concerned that if someone were to follow this over the long term, there are many different nutrients that they would be missing that you would normally get by eating regular food," he told "Good Morning America."

Cookie consumption as a weight-loss strategy is just another fad diet, says Dr. Stuart Fischer, who wrote "The Park Avenue Diet."

"Every study shows that when people change foods only and rely on that to lose weight, they have a 95% failure rate. This diet relies on sweets but to lose weight you need to forget what sweet tastes like. When you lose your sweet tooth, you are about a quarter of the way toward success."

Dr. Sanford Siegal developed the cookie diet in 1975 as a way to treat obese patients. He told ABC News he has treated more than half a million patients with the diet and that there is less risk of obesity in the very low-calorie diet. .

"I have yet to see the first case where anyone suffered any ill effect from eating a low-calorie diet," he told ABC News.

"It just doesn't exist." But Fischer says the diet is so low in calories that followers won't have the energy to exercise, which he says is important for heart health. And, he says, staying on a cookie-heavy diet results in a rebound phenomenon.

"The body goes into a starvation state," Fischer explains. "And it holds onto every morsel and calorie until the person's weight goes higher than it was before."