This year, Sharon says she's chosen to do it all over again, but this time, she's competing again a group that's more than doubled in size.
"When it [Rotorua Group Challenge] first started there was about 12 people. Now there's 167 people in this challenge. When I turned up to weigh in on Sunday night I couldn't believe it. There were queues. I ended up helping out. And when I turned up on Tuesday, it was like a mini concert. All these people were waiting for something to happen."
Sharon says it may have been her friend, Sue, and the scare of approaching 100kgs that lead her to start training, but it's her kids that keep her motivated each week.
"They're so proud of me. I'd come home from a weigh in one night and I went upstairs and I cried. They came up and said, what's the matter? And I said, I've just lost four kilos, in a week. And they said, we're so proud of you. They high-fived me.
"They said, we don't care if you win the challenge, just please don't put the weight back on. I need to keep up with them, they're both so fit, and I wanted to be able to go outside with them and play games with them. Now we do."
Sharon is now training for the Rotorua Marathon in May, and we wish her the best of luck.
To find out more about the Rotorua Group Challenge visit their Facebook page.