Phillips, 48, of Sterling Heights, Mich., lost 54.47 percent of her weight, enough to beat Mike Morelli of South Lyon, Mich., and Tara Costa of New York City.
Phillips started the competition last fall at 257 pounds. She ended at 117 pounds on Tuesday night's season finale.
"When I started, learning how to exercise and work out, and incorporate good nutrition into my diet was hard," Phillips said. "Once I learned and got on-board, and realized how important it was, the easier it became."
Morelli, 19, finished the show with a body weight loss of 53.35 percent. His starting weight was 388 pounds. Morelli dropped 207 pounds and weighed in Tuesday at 181 pounds.
The 24-year-old Costa dropped 155 pounds after starting the show at 294 pounds. Her percentage of body weight loss was 52.72.
Morelli's 55-year-old father, Ron, finished fourth.
For Phillips, winning the competition had special significance for her family which is caught squarely in the middle of the country's economic downturn and Detroit's automotive crisis.
Her husband, Russell is in danger of losing his job if automaker Chrysler LLC goes forward with a plan to shut down its Sterling Heights assembly plant in 2010.
"This will give us a nice cushion," Helen Phillips told The Associated Press before hopping a flight from Los Angeles to New York for a Wednesday morning appearance on NBC's the "Today" show.
NBC is owned by General Electric Co.
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