Rosie Mercado had reached a high weight of 410 lbs. when she was told by an airline employee that she needed to purchase a second seat to fit on the plane.

The embarrassing incident was an ‘aha’ moment for the mom-of-three, who decided she needed to lose weight, and successfully dropped to 300 lbs. through diet and exercise alone over the course of a year and a half.

Then, she reached a standstill, and even began putting on weight again.

“As soon as I hit 320, I was like, no I cannot go back to being 410,” Mercado, 36, tells PEOPLE. “I was going back and forth with my weight, and I saw a documentary on the [gastric] sleeve. I said, ‘You know what I’m going to do this. It’s the next part of my journey.’ ”

The curvy model said the real work came after having her surgery done.

“I don’t think you could be prepared for the work that has to be done psychologically,” she says, noting that she had to completely eliminate soda, dessert, pasta and rice from her diet, or else she felt extremely ill.

“Anything that bloats just completely went away,” she says. “You start really educating yourself on eating healthy, eating lean and eating really small portions. You go out with friends and you order an appetizer and eat half of that, and you sit there waiting for everyone else. It psychologically plays with your mind.”

Oscar Picazo

It took Mercado a while to get used to her new lifestyle and her new body.“You have to deal with being low-calorie, and deal with the adjustment to your body as you’re dropping weight,” she says. “You learn what you’re allowed to do and what you’re not allowed to do. If you do what you’re not allowed to do, you’re going to feel like crap.”

Choosing to get gastric sleeve surgery was a “tough decision,” says Mercado. “It’s not an easy walk. Surgery is just a tool. It’s not guaranteed success. Success comes from the discipline – it forces you to wake up and pay attention to what you’re eating. It’s a lifestyle.”

Mercado got the surgery to get healthy – not to be super thin.

“There’s no goal for me to be a size 6,” she says. “I just want to be healthy and fit. Being obese is putting your life at risk every single day.”

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