Donahoo, now 27, began her journey in 2010 after enduring a series of medical problems stemming from her 288 lb. weight.
"I was extremely tired all the time," says the project manager from Florida. "I also was pre-diabetic."
Keeping track of her calories via Livestrong.com helped her shed a staggering 137 lbs. – and feel fabulous.
"Eighteen months ago my son Zach gave me a hug and said, 'Mom! I can reach my hands all around you.' I started bawling because I never realized that he could never completely hug me," she tells PEOPLE.
Fernandez – who used to be 251 lbs.– also loves the effect that her incredible 126 lb. weight loss has had on her children.
"My kids Tyler and Sophia like to be active," says the 33-year-old director of communications. "Being so overweight kept me from doing all those fun, physical activities with them. The realization I wasn’t giving them the best was a huge motivator."
Since joining Jenny Craig in 2011, she loves hiking with her kids near their Georgia home and is even training for a marathon.
"The way I feel now is better than any food I gorged on before," she says.
For more of about the women's inspirational transformations – and to see more amazing weight-loss success stories – check out PEOPLE's Half Their Size issue, on newsstands Jan. 2, and tune in to the special 20/20 and PEOPLE Half Their Size airing on ABC on Jan. 4 (10 p.m. ET)