At 203 lbs., the Texas tween struggles with hypothalamic obesity – a rare, irreversible condition that leaves her feeling constant hunger pains but unable to lose any weight. In the past two-and-a-half years, Alexis has added 151 lbs. to her 4'7" frame, making it hard for her to move and live her daily life without help from her family.
In this exclusive PEOPLE video, above, Alexis and her mother, Jenny Shapiro, 34, share how life has changed for the once "active, happy kid" and how they hope a gastric bypass surgery will mitigate Alexis's extreme weight gain.
"It's such a danger to be this size," says Jenny, whose daughter's surgery is scheduled for March 21. "If we don't do anything about it, she is going to die from all the weight that she has gained and continues to gain."
Heartbroken at being unable to help their daughter, Jenny and her husband, Ian, 34, researched possible treatments and eventually found Dr. Thomas Inge, who has performed gastric surgery on other obese adolescents as the director of Surgical Weight Loss Program for Teens at Cincinnati Children's Hospital Medical Center.
"Gastric bypass tricks the brain into thinking it's full and can help cancel this insatiable hunger," according to Dr. Inge, who will perform the operation and has started a registry for hypothalamic obesity disorders.
Thanks to a popular online crowd-funding campaign that raised $78,000 to help cover surgery expenses, Alexis says she is "scared and excited" for the upcoming operation – and for the positive changes that could result from it.
For more on Alexis Shapiro's incredible story and her family's fight to give her a normal childhood, pick up this week's issue of PEOPLE.