Clueless star Elisa Donovan's eating disorder battle was so bad while she was making the cult 1995 movie, she almost died of a heart attack.The actress made the shocking confession during an appearance on the Celebrity Catch Up: Life after That Thing I Did podcast, revealing she was in denial about anorexia while playing dizzy Amber, opposite Alicia Silverstone, in the film."I had maybe three or four days off in one week, and I almost had a heart attack," Donovan explained."The doctor started talking to me about eating disorders, and I said, 'Well you're crazy', because I thought I was too fat to be anorexic," she recalled."At that moment, I was so afraid I was going to lose my job. My life had started taking off in the way I wanted it to with my career, and I was concerned that this was now suddenly going to prevent me from that," Donovan went on.Her ambition prompted her to seek help - and she's glad she did."Initially, the only reason I started to really get help was because I was worried I'd not be able to continue, but ultimately, that's not what helps you to recover. It has to come from a more pure place of wanting to be better," she shared."Clueless changed my life in a lot of ways," she added, revealing: "It helped me to get healthy."Now, at 50, she has become an advocate for others struggling with eating disorders."Having an eating disorder is rarely greatly understood by the general public, and it really is a mental and emotional disease. People just look at the body as if that's the issue, but it's actually not much about that at all. So I try to help as much as I can," she said.