35 to 40 percent of a child's body mass index, or BMI, is inherited from their parents. This according to a new study from the University of Sussex in England. For the most obese children, the number rises to 55 to 60 percent. Examining the height and weight data of 100,000 children and their parents from the United Kingdom, the United States, China, Indonesia, Spain and Mexico, results show that more than half of obesity is determined by genetics and family environment. Dolton said, "These findings should make us rethink the extent to which obesity is the result of family factors, and our genetic inheritance, rather than decisions made by us as individuals."