It's a lighthearted contest, Gonzalez said, and volunteers usually participate to help give them an extra incentive to drop unwanted pounds.
She, however, had more serious motivation.
About three years ago, her nephew Daniel Foster, 21, was diagnosed with focal segmental glomerulosclerosis, a disorder that often leads to kidney failure.
"It came out of nowhere," she said. "He was very healthy his whole life; when he got sick, we didn't know where it was coming from."
Last year, doctors in Foster's native Virginia told Gonzalez she was a match to give him one of her kidneys.
The only thing holding her back was her weight. At the time, she weighed 242 pounds; donors can't be heavier than 200, she said.
"When I went into work the next day, I saw the flier for [the contest], and just grabbed it," she said.
What followed were 13 weeks of dedication and sacrifice: Weighing "everything I ate," going to Weight Watchers meetings and keeping a detailed food journal.
By the end of the contest, held between April and July, Gonzalez weighed in at 170 pounds.
She said her nephew is "back to his old self" after his surgery in November, and that she's continued to drop weight and stay healthy.
"This will be ongoing forever with me; I know I'm a food addict," she said. "But if I set myself little goals - lose half a pound here, a quarter of one there - I know I can stick with it."
And yesterday, a beaming Gonzalez was presented with her prize, a new microwave that she says she'll share with her co-workers in the police communications unit.
On Twitter: @Vellastrations