Lady Gaga's 'Joker: Folie à Deux' co-star Joaquin Phoenix said she lost 'a lot' of weight for it. Here's what to know about her diet and fitness routines.

Lady Gaga has made clear that she can do it all—crush it on-stage with her impressive vocals and then blow you away on-screen. Her next big role is Harley Quinn in the Joker sequel Folie à Deux ...

Lady Gaga's 'Joker: Folie à Deux' co-star Joaquin Phoenix said she lost "a lot" of weight for it. Here's what to know about her diet and fitness routines.