"I thought, 'I can't go in there,'" she said. "But I made myself turn around, and I did it."

The accumulation of small steps like this one has helped Johnson lose almost 158 pounds in four years. But her battle with obesity has been a long one.

"I have been chubby since I was a little girl," said Johnson, who is a realty specialist for the U.S. Forest Service in Portland, Oregon.

Over the years, Johnson tried to lose weight. She joined and quit the Weight Watchers program twice -- losing weight only to gain all of it back and more. But something about the Weight Watchers method -- which focuses on portion control and physical activity -- kept her coming back.

"The first two times I joined Weight Watchers I didn't think about why I needed to lose weight, I just wanted to lose it," Johnson said. "Back then, the doctor told me my weight could affect my health later in life, but he didn't go into detail -- and I didn't ask. I didn't feel like there was a threat; so I continued to eat, and I wasn't active."

When Johnson joined the program for the third time, she felt bad -- physically. Her body ached. Her knees were throbbing as she walked into the program meeting.

"I finally started to think about the effects -- I could end up with heart disease, diabetes; all these things that I didn't think about before," she said.

The final straw was when Johnson's doctor put her on blood pressure medication. "I did not want to go into retirement with a medicine cabinet filled with prescription medications," she said.

Johnson chipped away at her weight-loss goal piece by piece. She never thought about how far she had to go; she only told herself that she would never quit again.

Four years later, Johnson is one of the fit and slim people she first revered at the gym. No longer on her blood pressure medication, she feels like she has regained control over her life and her future.

"People say to me, 'Oh, you have so much willpower,'" Johnson said. "I don't think it's willpower. I just care a lot about myself. While I'm on this earth, I want to feel good and be healthy."