Madonna's husband Guy Ritchie went on the Cookie Diet ... and stopped wanting to have sex with her as a result, she told a Phoenix radio show recently.

"My husband went on that Cookie Diet, and it was such a turn-off because he didn't want to have sex," she told "The Johnjay and Rich Show."

The 800-calorie-a-day diet — reportedly tried by Kelly Clarkson and Jennifer Hudson — did help Richie drop the pounds.

"He did lose weight, but he didn't really need to lose that much weight. I think he did it because all his friends were doing it and he wanted to see if he could do it."

Sanford Siegal, the doctor who created the Cookie Diet way back in 1975, responded Monday to Madonna's comments, saying that he has "treated more than 500,000 patients" and he "can't recall any of them reporting a similar effect on their sexual appetite."

He added, "In the case of my cookies, they taste good enough but I can't imagine anyone preferring them to sex."

Madonna's new album "Hard Candy" debuts April 29.