From first lady Michelle Obama boogying on a school field to chef Jamie Oliver taking on cities in 2010 and 2011’s Food Revolution TV program,we encounter the phrase “childhoodobesity” so often that it rarely makes a conscious dent. Statistics tell the sorry tale: Since the 1980s the number of obese children in America has tripled, and it affects 17 percent of all U.S. adolescents.

Almost one in three kids are overweight or obese, placing them at a significantly greater risk for heart disease, asthma, certain cancers, and type 2 diabetes, as well as psychological issues including low self-esteem and depression. Given youth culture’s current trifecta of physical inactivity, prolific calorie- and sugarpacked snacks, and an average four-plus hours screen time per day (which include abundant, targeted junk-food ads), fighting childhood obesity may seem like an impossible task. But, incredibly, the tides may be turning.

Researchers from the Robert Wood Johnson Foundation recently noticed that between 2006 and 2011, the number of overweight and  obese children in two major cities decreased: Philadelphia’s levels dipped by 4.7 percent and New York City’s dropped 5.5 percent. After obesity’s decades-long upward trajectory, these small but significant victories triggered cautious hope among health experts. Why are rates dropping? What’s working in this massive national health challenge? And where should we focus future efforts? Here, three inspiring influencers tackling obesity in their communities offer wisdom and predictions.