No one knows this better than the volunteers at Project HEALTH's Girls' Fitness and Nutrition (FitNut) Program. They are all female, and act as health and fitness mentors to overweight and obese girls in low-income communities across the country.

"Before children can succeed at school and other activities, they need to be healthy," said Lindsey Olier. She is a FitNut program coordinator, and history and science major at Harvard University in Boston. "Poor health negatively impacts all aspects of life."

Project HEALTH is an organization that engages college students in public health interventions designed to break the link between poverty and poor health. It partners with urban medical centers, universities and community organizations.

FitNut is one Project HEALTH program. It provides weekly after-school sessions for girls ages 8 to 12. In a supportive environment, the girls learn healthful eating and exercise activities. They develop healthful lifestyle habits, and grow up with health knowledge and self-confidence.

Olier volunteers at the Boston FitNut program, which is held at the Orchard Gardens Community Center in Roxbury, a high-minority neighborhood where more than 35 percent of children live below the poverty level.

The Massachusetts Department of Public Health and Boston Public Health Commission report that 61.8 percent of African Americans in Roxbury are obese. Only 31.2 percent of the area's Caucasians are obese.

"I want to help change these girls' lives," Olier said. "Although children don't have complete control of their nutrition and fitness lifestyles, I want to teach them to make smart decisions when it counts. I want them to pick a granola bar instead of a candy bar at the school snack machine."

The results of the program have been stellar. After taking part in the program, 75 percent of FitNut participants "strongly agreed" or "agreed" that they were thinking more about what they ate. Sixty-seven percent of parents and guardians said their children are "more motivated" because of the program.

The best response? According to Olier, it's something a little more hands-on. "The best feedback we get is when the girls tackle us with big bear hugs at the beginning of each program because they're so happy to see us," she said. "We are a real presence in their lives."