Uploading two side-by-side images of herself before losing a total of 60kgs, Alessandra can be seen grinning widely as she poses for the camera in both images.
"2006 vs 2021," she captioned the post, before directing a question to her fans.
"Do you remember me like this?" she wrote in Spanish.
The post comes after Alessandra spoke to Woman's Day to reveal she has struggled with obesity for years, before undergoing a gastric bypass surgery in 2008.
"It was such a transformation both physically and mentally," Alessandra said.
"My decision to do it had nothing to do with aesthetics, I did it for my health, and at the time I was married and I was thinking about having kids and I had learned about the complications of trying for a baby with that extra weight, so I made a decision," she explained.
Alessandra also told 9Entertainment that she travelled to Colombia to undergo the surgery, and subsequently lost 60kg.
"My surgeon was the best and I thought I will go where he lives and travel to Colombia and have my surgery there, and it was life-changing in many, many, many positive ways — most of which is of course my health, which has been incredibly good since I had the surgery," she said.
"With that surgery you lose weight and because I work in the media that became a big part of the story."