In an interview on This Morning, Joan, 83, recalls how she took little green diet pills - which curb appetite - because she was "too fat", reported OK! magazine.
"When I first went there I was about nine stone (57 kgs) and the studio said, 'You're too fat, you have to lose weight.' But it was hard to do, I was 20, and I loved my food, so they gave me these little green pills.
"I took them every morning. Goodness, I didn't want to eat - I didn't sleep much either! A friend came over and said, 'What are you taking, you never eat when we go out. He said, 'You can't take these, they're Dexedrine, that's what hooked Judi Garland'," she says.