On a recent day, Maria Velasquez led 25 women in outdoor aerobics at a park in this city's rough southeast district, home to a large farmworker community.
Nearby, young children played noisily on well-clipped grass. Wiping sweat from her brow, Velasquez announced she'd lost 80 pounds and, with it, a high risk of diabetes.
Elena Marin, who picks grapes and lemons, said she came to Stiern Park three times a week and had lost 20 pounds, with 80 to go. Sonia Molinar, who has shed 15 pounds, said that two years ago she wouldn't go near the park, which was home to drug users, stray dogs and gang graffiti.
Then neighbors and community leaders banded together to clean it up. Now the women walk in the park five mornings a week. Molinar brings her daughters.
"You keep yourself healthy and you make friends," she said. "Everything is good."
Health advocates point to the park's transformation as a success in their new initiative to stem a growing epidemic of obesity in the Central Valley.
The national obesity rate has risen for decades, increasing from 15% of the population in 1976 to 33% in 2004, according to the U.S. Centers for Disease Control and Prevention in Atlanta.
In the Los Angeles metropolitan area, more than 58% of residents are obese or overweight, according to a CDC report. The rate is higher still in the farm-rich Central Valley, said organizers of the Central California Regional Obesity Prevention Program, despite an abundance of fresh produce.
"We supply the country with cheap food, but the benefit does not come back to us," said Edie Jessup of Fresno's Metro Ministry, a nonprofit working on the issue.
Nearly two-thirds of the people living in Merced, Madera, Fresno, Tulare, Kings and Kern counties are obese or overweight, according to the Central California program. More than a third of the region's fifth-, seventh- and ninth-graders have unhealthy weights, a major increase from a decade ago. Armed with statistics, public health directors in the six counties joined with community groups to try to turn the situation around.
Organizers of the Central California Regional program say that if communities are to succeed in reversing the trend, leaders need to look not only at what people eat but also at where they live.
Access to safe parks and recreation programs is critical, said Jennifer Lopez, a community worker who helped the Stiern Park group navigate City Hall.
Also key is making sure fresh produce is easy to buy in neighborhood markets. A recent UCLA study said that the highest obesity rates are in lower-income areas in which convenience stores and fast-food outlets predominate.
"If they don't have programming, parks and easy, convenient access to fresh foods, they will make unhealthy food choices because that's what is available," said Veva Islas-Hooker, director of the Central California program.
Overweight and obese adults are more likely to develop diabetes, heart disease and certain types of cancer.
As part of the Central California program, each county set up its own obesity prevention council and got to work, Islas-Hooker said.
In Fresno, for instance, zoning laws made it difficult to create a farmers market in the city's low-income southeast area. Community groups got the City Council to make changes, said Jessup of Metro Ministry. After three major supermarkets pulled out of the area, the community groups also began trying to lure small markets with fresh produce.
Fresno Unified School District appointed a physical education director, a position that did not previously exist.
In rural Tulare County, Earlimart and Pixley schools agreed to open play yards after hours. In Kings County, a Kettleman City school district opened school grounds as a community park. Several counties have petitioned the federal government to allow food stamps to be used at flea markets, where people can buy cilantro, chiles and other fresh produce, Islas-Hooker said.
Some people respond enthusiastically to the idea.
In southeast Fresno, Stephanie and Gustavo Gonzales, who have six young children, had just bought fruit juice at a convenience store near their home when they were asked if they would like to see a farmers market in their neighborhood.
"I'd buy bananas, strawberries, grapes and nectarines," Stephanie Gonzales said. "And avocados, chiles and tomatoes. It would be easier, and healthier too."
But Anthony Curiel, 9, and Angel Ochoa, 7, emerged from the store minutes later with a super-sized soda and a large bag of Flamin' Hot Cheetos. Both were dubious about swapping their snack for something from a farmers market.
"I wouldn't go," Angel said.
"Unless they had Cheetos!" Anthony added.
Health advocates say many low-income Central Valley children don't have adult role models when it comes to healthful food and exercise.
That's why projects like transforming Stiern Park are so important, said Lopez, the Bakersfield community activist. Once the neighborhood women got energized about cleaning up the park, they gained confidence to make other changes, she said.
They organized about 100 neighborhood volunteers and applied for a $10,000 grant from the Chamber of Commerce, then used it to put in a concrete walking path. Now they take their walks on that path.
Lydia Ortiz said vigorous exercise helped her lose 28 pounds -- and the need for the insulin, her doctor told her.
"I've never seen a doctor jump up and down," said the mother of two. "She was so happy."