Reporter: At 308 pounds, jen larson dreamed about getting skinny. I fantasized about it, yeah. It's the fairy tale of weight You lose the weight and you're beautiful and you're happy. Reporter: In her... See More
Reporter: At 308 pounds, jen larson dreamed about getting skinny. I fantasized about it, yeah. It's the fairy tale of weight You lose the weight and you're beautiful and you're happy. Reporter: In her pursuit of happiness, she lost a staggering 180 pounds. Larson says she's battled weight problems since childhood and tried just about every diet but when nothing worked, she turned to bariatric surgery. I saw the before and after photos and I leapt into it. I had tunnel vision. All I could see was this idea of me being thin. Reporter: That's exactly what happened. Did you find yourself becoming more obsessed with your weight when you were thin? Absolutely. You know, being thin didn't make me happy. I'm still looking in the mirror and still hati I see and how is this even possible? Reporter: Dr. Bethany marshall says many people believe losing weight will solve their problems. Obese people live with the fairy tale or the illusion if they lost the weight their lives would be better. But what happens is when they lose the buffer, they feel that people are scrutinizing them. Reporter: In her new book "stranger here" larson says she was finally forced to face her real issues. I had to deal with my real psychological struggles. Reporter: You have depression? Oh, yeah. Reporter: Larsen says she doesn't regret having the surgery and hopes others will look beyond their body size to find true happiness. I want to not have my goal be a size and a number. I want my goal to be able to be strong and to run a marathon and to be comfortable in my skin. Reporter: Are you happy now? I am. I'm pretty happy. Reporter: For "good morning america," abbie boudreau, abc news, salt lake city, utah. All right, our thanks to
This transcript has been automatically generated and may not be 100% accurate.