At 115 kilograms, a combination of grief and unhealthy lifestyle choices had caused the Emerald resident to plummet into what she describes as 'black hole'.

It started about five years ago, when she had to deal with the deaths of her 13-year-old niece, her father and her best friend all within a year.

"I thought I was coping but when I look back I wasn't," she said. "I've always been a strong-minded person but I began to drink, eat, and smoke more to cope."

The turning point came when Ms Hoffmann's eight-year-old daughter Jorja took a photo of her sitting outside with a cigarette dangling from her hand. She barely recognised herself.

"It was such a shock to see how unhealthy I looked."

Ms Hoffmann made a promise to herself to change her life. Last year, she began the Michelle Bridges 12-week body program and joined the Fitlife gym in Ferntree Gully.

Since then she has lost nearly 40 kilograms.

This April, to mark what would have been her niece Stacey's 18th birthday, Ms Hoffmann is undertaking a fitness challenge to raise money for the Heartkids foundation. The foundation supported her niece during her battle with cardiomyopathy.

"If we can't throw her an 18th birthday party - then this is the only way I know how to help," she said.

Ms Hoffmann will be completing a thousand burpees - a cross between a jumping jack and a push-up - in an hour.

"I chose burpees because they are one of the physically hardest exercises for me to do. These kids have no option have to endure hours and hours of pain and if I can't endure one hour then that's a weakness."

Hoffy's Burpee Challenge is on at 11am on Saturday, April 14, at the Ferntree Gully Hotel. Details and donations: Click here or call 0488191119.