Monica Rose Villarreal, who tipped the scales at 143 pounds at age 8, embarked on a new career as an ultrasound tech in 2007 after losing her job due to the recession. But the life she saved ended up being her own, she tells People.

“I envisioned scanning babies and telling people, ‘It’s a girl!’ and having this fun time,” she says. So Villarreal enrolled in the 18-month training program and found that “in order to scan babies inside of the human body, you have to learn how to scan. So we practiced on ourselves.”

And at 310 lbs., Villarreal became a popular test subject in class—“it was a joke, like, ‘She has no neck, it’ll be hard to scan her arteries going to her brain.’ “

“This is where I actually got to see with my own eyes that my organs were smothered in fat, covered in it. And then I’m learning about how this impacts your health and it just became glaringly obvious that I was a walking, ticking time bomb,” she says. “I said to myself, ‘I’ve got to do something.’”

Read the full article on People.