Last summer, the 'Bridesmaids' star confessed to feeling "sad" that it took her until her forties to lean into healthier living.
Rebel said: "Now that I know I can do it, sometimes I feel sad that I didn't do it earlier."
She went on to label herself a "late developer" and expressed that she longed to have "tried when I was 30, not 40."
However, she pointed out: "But everybody's journey is different, and it's not a race or competition. I have a natural empathy for anyone who struggles with weight issues because that's something I've always struggled with."
Meanwhile, Rebel recently admitted her team were opposed to her decision to embark on a "year of health" because she'd been so successful playing the "funny fat girl" in a string of movies.
She explained: "I got a lot of pushback from my own team actually, here in Hollywood, when I said OK, I'm going to do this year of health, I feel like I'm really gonna physically transform and change my life.
"And they were like why? Why would you wanna do that? Because I was earning millions of dollars being the funny fat girl and being that person."