(CNN) -- Alan Gamez remembers the sadness he used to feel just looking in the mirror.
"My stomach was huge," said Gamez, now 18. "I would just look at myself and be disappointed."
Obese throughout childhood, Gamez weighed 270 pounds his freshman year of high school. He felt like he had no friends that year.
"I would overeat because I really had no social life in school," he said.
He decided not to play baseball as a freshman because he thought his weight would hinder his performance.
"He was unhappy in all aspects of his life, and he took it out on his physical well-being," Gomez's high school counselor Mary Abbott wrote in a letter nominating Gamez for the Denver Mayor's Youth Award. "Alan had no control over his life. Thankfully, this is not the Alan Gamez of today."
In his sophomore year, Gamez decided to make a change. It started when he took an exercise health and wellness class, which taught him about nutrition and exercise. He remembers entering this class "a little shy," but became interested in the basics of working out and eating right.
The hardest part, he said, was overhauling his eating habits.
Gamez was accustomed to eating a lot, and often -- eight times a day. His mother would make enchiladas or fried beans; in between meals, Gamez would snack on ice cream or chips.
"It was just what made me feel good," he said.
Determined to change, Gamez stopped eating red meat and got his protein instead from chicken and fish. He made sure his caloric intake was between 1,500 and 2,000 calories each day.
Once his mother noticed a change in him, she started cooking differently, too, Gamez said. His mother would go to his meetings with his dietitian, and the conversations opened her eyes about making better food choices, Gamez said.
At first, Gamez was too shy to even run around the block near his home. Every morning he would privately exercise in an alley near his home.
"I would really not see changes in me," he remembers. "I would still believe I was obese and stuff, but every time I would go out to a family party, people would tell me, 'Wow, you've changed a lot.' I really didn't see it until I started noticing that I had to buy new clothes."
In about four months, he went from wearing clothes sized 2XL down to large, and eventually down to a medium. His pants size shrunk from 42 to 36, and then from there to 32.
"After a year, when I went back into school my junior year, that's when I thought I was -- not perfect -- but I felt comfortable in my body," he said.
By the first semester of his junior year, he had dropped 100 pounds, weighing in at 170 the first semester.
The change wasn't only physical. Gamez joined the baseball team at a high school nearby and started hanging out with the players. He found that more people were talking to him.
"I told some people what I was doing so they could change their ways as well," he said.
His now-girlfriend didn't notice him when he was at his heaviest, but after he lost weight, he started talking to her. She liked what Gamez did to combat his weight problem, he said, and the two have been together since junior year.
"My confidence went up drastically," he said.
In the spring of 2013, Gamez was honored with the Denver Mayor's Youth Award, which celebrates teens who have overcome adversity and made positive changes. He was given a $1,000 scholarship.
These days, Gamez works out at least five days a week, mostly lifting weights. Monday, he'll work his chest and back; Tuesday is biceps and triceps; Wednesday is cardio; Thursday is shoulders; and Friday is legs.
On weekends, he'll be active too -- running, doing cardio exercises or playing catch with his girlfriend.
He has gained weight since the end of high school -- he's up to 230 pounds -- but he's focusing on building muscle. He knows that extra pounds will come with that. Once he reaches his muscle goal, he'll go back to cardio exercises.
Gamez is now a student at Colorado State University. He wants to major in something like nutrition so that he can help others do what he did.
"He told me there is nothing greater than to watch people transform and reach their goals, knowing that they have the power to change within them," Abbott wrote.