Background/Objectives: The aim of this study was to examine the discrepancy between nutrition-related knowledge (NRK) and nutrition-related practice (NRP) among 1440 Polish school-aged students (10–18 years), according to BMI status, and to identify factors associated with this discrepancy. Methods: This cross-sectional study was conducted via the CAWI method using an author-developed, non-validated questionnaire. Questions assessing NRK and NRP were thematically aligned and referred to the recommendations of the Polish Healthy Eating and Lifestyle Pyramid for Children and Adolescents (aged 4–18 years). Results: Students with excess weight scored significantly lower in nutritional knowledge (NRK: 46%) and practices (NRP: 30%) than those with underweight or normal weight (NRK: 52–53%, NRP: 33–34%). Higher NRK was associated with older age, female sex, larger urban residence (for students with overweight and obesity), and higher maternal/legal guardian education level (for students with normal/underweight body weight). Better NRP was associated with higher NRK and higher physical activity, while rural or small-town living was positively associated with healthier dietary practices and maintenance of normal BMI. Conclusions: The present study confirms that nutritional knowledge is a necessary but insufficient condition for shaping appropriate dietary behaviors among adolescents with different BMI statuses; lifestyle factors, practical food-related skills—including self-assessment of knowledge and adherence to dietary recommendations—and the broader environmental context plays a crucial role. These findings highlight the need for targeted nutrition education programs that expand not only knowledge but also practical skills among students.
Wawrzyniak et al. (Mon,) studied this question.