TROY, Mich. -

A Troy mother dropped 100 pounds after 20 years of trying but says people have to really want to lose the weight before any exercise and nutrition program will work.

Kathy McDonald, 42, said she became more depressed and discouraged as her problem of being overweight quickly spiraled into an obesity problem. She said at her highest point, she weighed 281 pounds.

"I would not leave the house. I avoided any kind of function, school reunions, even going out with my girlfriends I would always come up with an excuse because I didn't want to be, you know, the big girlfriend," said McDonald.

She explained she's blessed to have a husband and three boys that love her no matter what her weight is, but said her weight affected them horribly.

"They weren't embarrassed about me or my size, but they were often put into positions where like if I went to their school they would get teased and that put them in a position where they had to defend me," said McDonald.

McDonald said being teased at school about their mom's weight was not the only way her weight affected her children.

She admitted, "I wasn't eating healthy. I didn't feed my children something healthy and me go and have something bad. This is how we ate."

McDonald said she tried to lose the weight for 20 years, but was never able to do so. Her doctors warned her that she was headed for serious health problems, even death, if she didn't change her lifestyle.

McDonald said a turning point for her happened on a trip to Cedar Point where she tried to ride a roller coaster with her son. She couldn't fit and they were kicked off the ride.

"We literally had to get out of the seat and walk in front of all those people and it was just humiliating," said McDonald.

Desperate to get her life back, McDonald decided to try losing weight again. McDonald discovered P90X, a weight loss program she said offered her cardio and weight workouts, nutrition plans, and constant support.

For the first time in 20 years, Kathy began shedding the pounds.

She said her success was due to the combination of having a structured workout, nutrition plan, endless support and most importantly, the drive to lose the weight.

One year later and 136 pounds lighter, McDonald stresses that regardless of what weight loss program you choose, the key is being ready and committed.

Her success at losing the weight paid off literally, she recently won $100,000 in the Beachbody challenge in Las Vegas.

McDonald said her weight loss has inspired her husband to lose 100 pounds. She is also motivating others; as a Team Beachbody coach she is helping 200 people lose weight.

For more information on P90X, the program McDonald used, click here.