The "Pitch Perfect" star told "BBC Breakfast" she decided to lose weight for her health, but she got pushback from her own management ... They questioned, "'Why would you wanna do that?' Because I was earning millions of dollars being the funny fat girl and being that person."

Rebel says, although she was always comfortable with her weight, she found comfort in food to escape her emotions as she struggled to establish herself as an actress.

She says she knew that she needed to make a change... "I knew deep down inside that some of the emotional eating behaviors I was doing was not healthy. Like I did not need a tub of ice cream every night."

Last November, Rebel revealed she reached her goal weight of 165 lbs ... partially due to the Mayr Method diet plan, which cuts sugar and encourages slow eating. She's also become something of a gym rat ... working out 6 times a week.