According to the National Health and Nutrition Examination Survey in 2007, nearly half of all American children are either overweight or obese. Retrospective chart review identified patients with the diagnostic codes for overweight, obese, and/or excessive weight gain. Inclusion criteria were current age between 2 and 20 years, a minimum of 5 visits with weight and height measurements, and a body mass index (BMI) at or above the 85th percentile. A total of 184 patients met inclusion criteria. More than half the children became overweight before age 2, and all patients were obese or overweight by age 10. The rate of gain is approximately 1 excess BMI unit/year, therefore causing most children to be overweight by age 2 (R (2) = .53). This study indicates that the critical period for preventing childhood obesity in this subset of identified patients is during the first 2 years of life and for many by 3 months of age.