Several indices for body-weight disorders exist in scientific literature, but it is inconclusive whether or not they can yield comparable results when applied to Nigerian children. The prevalence of weight disorders in Nigerian children was examined using the Centre for Disease Control and Prevention (CDC) body mass index (BMI) for age charts and the International Obesity Task Force's (IOTF) age- and sex-specific BMI cut-off points. Participants were 2015 pupils (979 boys and 1036 girls) aged 9–12 years, attending 19 public primary schools in Makurdi, Nigeria. Stature and body mass were measured using standard techniques. Results were analysed using student t-test and Chi-squared statistics, with the probability level set at ≤0.05. CDC's BMI charts categorized 2.1%, 1.6% (boys) and 3.2%, 2.8% (girls) as overweight and obese respectively. Corresponding data for the IOTF's BMI charts were 1.7%, 0.9% (boys) and 2.6%, 2.0% (girls). CDC cut-off points indicated higher prevalence of overweight and obesity, thus suggesting the need for a single definition for evaluating measurements of body mass-for-stature in the children. However, more disconcerting is the fact that CDC charts showed a high prevalence of underweight for the boys (87.1%) and girls (79.7%). Prevalent underweight conditions in our sample need urgent intervention. The IOTF method is limited in its utility to identify children who are underweight and may be at risk of growth faltering.