ET also reports the singer had undergone gastric sleeve surgery.
"She truly feels her weight loss surgery paid off because she is at her happiest when she is thin," the source claims.
“She has always struggled with her weight. In the last five years it has become more and more difficult for Mariah to shed the pounds," the source says. "She has a huge career, children, and she has been through big changes with her team. It's truly been an emotional roller coaster and that always affects her weight, both gain and loss."
“Mariah is known for her yo-yo dieting. When she has a big project coming up, she works so hard to lose weight. She often becomes incredibly stressed out and barely eats. Then the moment her project is complete, she lets loose and enjoys all her favourite foods, champagne and the weight gain returns," the source claims.