Effect of a School Dietitian on Nutrition and Weight Control in High School Students: A School Case Study

Aim: This study was planned and conducted to determine the effects of nutrition education and individualized counselling provided by a school dietitian on high school students’ nutrition knowledge levels, dietary behaviors, anthropometric measurements, and body composition. Methods: This prospective educational intervention study was conducted during the 2024–2025 academic year among 255 students attending a public high school in Kayseri. Students received healthy nutrition education twice during the first and second semesters of the academic year, and the intervention was evaluated using a pretest–post-test design. Nutritional knowledge levels before and after the intervention were assessed using a 15-item multiple-choice nutrition knowledge test developed by Sarıdağ Devran; dietary habits were evaluated through a questionnaire; anthropometric measurements and body composition were assessed using the bioelectrical impedance analysis (BIA) method. Individualized nutrition counselling was provided to students when deemed necessary. Data were analysed using IBM SPSS Statistics version 22.0. Normality was assessed with the Kolmogorov–Smirnov test; the Wilcoxon signed-rank, Chi-square (χ²), and McNemar tests were used for comparisons. Statistical significance was set at p 0.05. Results: The study included a total of 255 students, comprising 136 boys (53.3%) and 119 girls (46.7%). The mean age of the participants was 15.76±1.12 years. The baseline mean nutrition knowledge score was 8.9±1.9. The mean body weight was 71.9±15.3 kg in boys and 59.4±12.5 kg in girls; the mean body mass index (BMI) was 23.0±4.4 kg/m² and 22.1±4.0 kg/m², respectively. The mean waist circumference was 81.2±11.2 cm in boys and 71.5±9.8 cm in girls. No changes were observed in meal patterns, and breakfast was identified as the most frequently skipped meal. Nutrition knowledge scores and levels increased significantly after the intervention (p 0.001). Among female students, significant reductions in body weight and BMI were observed following the intervention (p = 0.05). According to BMI classification, the proportion of male students in the normal-weight category increased (p = 0.486), while decreases in the overweight and obese categories were observed among female students (p = 0.031). Waist circumference increased in both male and female students (Girl: p = 0.004, Boy: p = 0.005). Evaluation of the waist-to-height ratio revealed a significant increase in the proportion of female students in the normal category and a decrease in at-risk groups (p 0.001). Body composition analyses showed increases in fat-free mass, fat-free mass percentage, total body water, and body water percentage, along with significant decreases in body fat percentage and fat mass in both male and female students (p 0.001). Conclusion: Nutrition education and counselling interventions led by a school dietitian improved nutrition knowledge and positively affected anthropometric measurements and body composition indicators among high school students. These findings demonstrate that the school dietitian model is feasible at the high school level and may contribute to school health services.