He told the book's author Maureen Callahan that Gaga's crash dieting went to such extremes she lost a staggering 20 pounds (9.1 kilograms) between the first and final fittings for a show outfit.
But the pop sensation's dance coach Laurieann Gibson has lashed out at David Ciemny's claims, telling UsWeekly.com, "I just want to say it's all foolishness. Why would anyone say that?
"Clearly you have nothing to do with these dynamics, creatively or really with the people that are working so hard. She doesn't have an eating disorder, and whoever is saying that is an a**hole. Quote me! We are fighting for our dreams. There's no hocus pocus there. The guy saying it has absolutely nothing to do with Lady Gaga."