Book excerpt: Obesity is a national epidemic in the United States. It is estimated that by 2018 the cost of treating weight-related illnesses will double to almost $350 billion a year, while a 2010 report by the US Surgeon General estimates that two-thirds of American adults and almost one in three children are now overweight or obese. This volume originated in a special 2009 symposium funded in part by a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and sponsorship from Mars WalthamA on how human-animal interaction may help fight obesity across the lifespan. The authors present scientific evidence about the benefits of dog walking for improving human and animal health, and case studies of programs that are using this powerful expression of the human-animal bond to combat obesity. The volume is especially valuable as a sourcebook of evidence-based studies for public health professionals treating overweight humans and veterinarians treating obese dogs.