As rates of obesity and type 2 diabetes continue to escalate, effective means of prevention become paramount in curbing the largest epidemic of our times. With adult obesity rates in the United States already at 34%, according to the most recent National Health and Nutrition Examination Survey (NHANES) data, preventing obesity in childhood is of increasing urgency. Exercise and lifestyle modification have been shown to be effective in adult trials for diabetes prevention, such as the Diabetes Prevention Program (DPP), Finnish Diabetes Study, and Da Qing Study. This article reviews randomized, controlled trials in children, using exercise and lifestyle modification in the prevention of insulin resistance and obesity. This review encompasses studies within the past decade from Planet Health in 1999 to the Beijing Obesity Intervention trial published in 2007 and covers both school-based and family-based approaches. A challenging task by any means, these trials have contributed valuable insight into the efficacy of various approaches toward preventing childhood obesity and insulin resistance, a pressing public health concern.