Assessment of Nutritional Knowledge and Body Mass Index Status among Students in Nigeria: A Cross-Sectional Study

Background The double burden of malnutrition coexisting undernutrition and overweight/obesity is a growing public health challenge among young populations in low- and middle-income countries. Nutritional knowledge plays a crucial role in shaping dietary habits that influence body weight, particularly during adolescence and early adulthood. Methods This cross-sectional study assessed the association between nutritional knowledge and body mass index (BMI) among 395 students (194 university and 201 secondary school students) in Nigeria. Stratified random sampling was used. Data on sociodemographic characteristics, anthropometry, and nutrition knowledge were collected via a structured, pre-tested questionnaire. BMI classifications followed WHO guidelines. Associations were assessed using chi-square tests and multinomial logistic regression. Results Students with good nutritional knowledge had significantly healthier BMI profiles, with lower prevalence of both underweight and obesity (p = 0.012). Age was also a significant factor: underweight was more common in students aged 10–19, while overweight and obesity were more prevalent in those 20 and above (p < 0.001). Monthly stipend and level of education were also significantly associated with BMI (p < 0.001). Multinomial regression indicated that good nutritional knowledge reduced the odds of obesity by 79.9% (aRRR = 0.201, 95% CI: 0.053–0.753). Conclusion Good nutritional knowledge is associated with healthier BMI among students. Age and socioeconomic factors also significantly influence nutritional status. Interventions should incorporate targeted nutrition education and economic support to reduce malnutrition and promote healthy weight among adolescents and young adults in Nigeria.