Current child measurements of weight status in Wales are determined at early childhood only. A further measurement at late childhood could identify adiposity levels prior to adolescence and young adulthood. The aim of this study therefore was to determine current adiposity levels in a cohort of children at late childhood and present a prediction of future levels upon entering young adulthood. In total, 288 boys (M age = 10.94 years, SD = 0.58) and 257 girls (M age = 10.78 years, SD = 0.63) from South East Wales were measured for anthropometry and their body mass index (BMI) (kg/m2) determined. International Obesity Task Force data predicted their BMI at age 18 years. Approximately one quarter of boys and girls in late childhood were classified at an unhealthy weight. Predictive data showed that by age 18 years, this percentage had increased to approximately one-third in both genders. The overweight and obesity levels in our cohort were high and predicted that many could become obese adults. This study therefore supports the call for the current Wales child measurement programme to be extended to report weight status in late childhood.