MIAMI -- Dieters may not be able to have their cake and eat it too, but one doctor says they can have their cookies.

A weight loss plan developed by a South Florida doctor has a special cookie as it's cornerstone.

While his patients sing its praises, critics raise concerns about its safety and long-term effectiveness.

In just seven months, Wendy Armstrong is a shadow of her former self. She said, "I've lost 72 pounds in seven months."

Susan Fox has lost 60 pounds in a year and says she has "never felt better."

The women attribute their dramatically diminished dimensions to Dr. Sanford Siegel's cookie diet.

Siegal says, "The idea is the patients eat these cookies through out the day. They're allowed one meal and the meal is dinner, but they eat these cookies in response to hunger. They have to eat six, and those six cookies plus dinner add up to 800 calories."

Critics say that's not enough.

Sheah Rarback, a University of Miami dietitian says, "800 calories a day is so far below what the body requires that you wind up turning to supplements, potions for nutritional support and you're getting into a dangerous ground."

Critics also charge that Siegal prescribes weight loss drugs, something he readily admits. "Some of our patients are on appetite suppressing medication in addition to the cookie," he said. "In fact probably over half of our patients are."

Fox is moving into the maintenance phase of the program that has no food restrictions but hefty exercise requirements.

Siegal says, "The idea is that we want our clients to burn up so many calories in exercise that they simply can't gain the weight back."

Armstrong's got another 25 pounds to go before she's reached her goal, and with cookies in hand, she's confident she'll get there. She says, "The weight comes off rapidly and it keeps you encouraged and it gives you the willpower to stay strong and keep going."