It sounds like the dream diet: Eat cookies every day and lose weight.
"They're not meals, they're not breakfast or lunch, they're for hunger the rest of the day," he said. "You have no meals up until dinner time. The cookie controls your hunger up until dinnertime, then you get to eat a very reasonable dinner."
Lynda Sells, who started the diet in May, eats six of the special cookies throughout the day when she gets hungry. In the evening, she eats a sensible dinner of lean protein and vegetables. And she said the diet works for her.
"I wanted to lose about 50 pounds, and so far I've lost 27 of that," she said.
Siegal said his diet cookies work by suppressing hunger.
"When I formulated this 34 years ago, the idea was to get the right mixture of amino acids, which are essentially protein substances that would control hunger," he said.
The weight loss comes from the low number of calories the dieters consume.
"We shoot for 1,000 calories a day," Siegal said. "Five-hundred of those calories come from the cookies, 500 comes from the dinner. Everyone loses weight when they eat 1,000 calories a day. There are no failures at 1,000 calories a day, I can assure you."
"If someone needs to lose a few pounds for a wedding or a cruise or to jam into a tuxedo for a high school reunion, whatever, then this is something that is going to appeal to them," said Pincus, who runs the To Life! weight-loss program
But the Cookie Diet will "ultimately fail" because people will stop eating the cookies, he said.
"So when you come off the Cookie Diet, if you don't have a system in place using the technologies that are now very clearly evident in the expert weight loss medical community, then you're going to gain the weight back," Pincus said.
Siegal said he recommends people work on ways to maintain their weight loss after they reach their weight goals by using the Cookie Diet.
A box of cookies for one week costs about $60. Sells said the price is well worth it.
"For years, I've tried every other diet out there and been on a rollercoaster of gaining weight and was at a point where I was heavier than I've ever been in my life," she said.