Chris Haston/NBCU Photo Bank
"When I started Will & Grace, I was a size 8," she told Jamil. "And what happened was, every time I would go in for a fitting, I couldn't fit into clothes. You know, 80 percent of it I couldn't fit into, and I would leave just hating my body and hating myself."
Revealing that the show's costumer designer told her not to worry about her weight, Messing said she still felt self-conscious whenever a larger size needed to be ordered for her over the course of her time on the show.
"I thought, 'My life would be so much easier, and it would be easier on everybody trying to do their job, if I just lost weight,' " she continued. "So I started doing yoga every single day and I did one of those meal delivery services. I started to get smaller and then I was a 6, and they were like, 'You're losing weight, you look amazing!' "
Patrick Randak/NBC Debra Messing
But the compliments about her physique caused Messing to think, "Oh, this is making them happy, so I should do more of it."
"Then I was lucky enough to be invited on the red carpet to the Emmys and the Golden Globes, and that was the same time that Ally McBeal was at its height and Calista was the 'It' girl and Portia de Rossi also was so, so slim, and she's spoken openly about her anorexia, so it's all within sort of the same theme," she recalled. "I would try to fit into these gowns and of course they weren't sample sizes, and it was like, 'OK, we have to let out the seams, etc.' "
"This was supposed to be the greatest time of my life, being nominated for best actress in a TV show I loved for an Emmy and walking on the red carpet. I walked out and I immediately felt so incredible, and then I was standing next to all of these other actresses who were half my size, and I felt fat, and I felt ugly," Messing continued.
Messing then told Jamil that she ultimately ended up getting down to a size 2.
"I was way too skinny," she confessed. "But, you know, going in for those fittings, I fit into everything. And all of a sudden, I literally could fit into anything that was high fashion. So all of a sudden, everything seemed to open up for me, because I was a 2."
"For a while there, I was maintaining that, and then I got sick," the star added.
Chris Haston/NBCU Photo Bank/NBCUniversal via Getty Images Debra Messing in Will and Grace
Jamil noted during their conversation that when Will & Grace premiered back in 1998, it was during "the height" of Hollywood’s hard-to-obtain beauty standards, before adding that "the physique of the ’90s" was to be "wildly" skinny.
"My body just could not hold out," Messing said. "My adrenals crashed, I was exhausted and it just became clear to me that I couldn’t be healthy and a size 2 at the same time."
Messing also said she wishes she had been kinder to herself and her body during that tumultuous time. "I look back at those pictures and I was beautiful," she shared. "I mourn the fact that that was my interpretation of reality and that was the torture that I put myself through."
If you or someone you know is battling an eating disorder, please contact the National Eating Disorders Association (NEDA) at 1-800-931-2237 or go to NationalEatingDisorders.org.