Changes in BMI and Fat Mass and Nutritional Behaviors in Children Between 10 and 14 Years of Age.

: Unhealthy nutritional behaviors and excess body weight constitute a serious challenge for public health in children and adolescents. The aim of this study was to examine changes in body mass index (BMI), body fat mass (FM), and nutritional behaviors in the same group of children during a 4-year observation between 10 and 14 years of age including the period of the COVID-19 pandemic. : BMI and FM using bioelectrical impedance were assessed. To assess nutritional behavior, a questionnaire on eating behavior was used. The study was carried out in a group of 250 children, starting from the age of 10 and finishing at the age of 14. The measurements were collected in the years 2017 and 2021. The results were compared and analyzed. : Excessive BMI (overweight and obesity) was more often found in girls (28.29%) than boys (23.63%), while normal body weight was more often found in boys (65.76%) than girls (60.96%). Between the initial and final assessments, the percentage of children with normal body mass decreased from 65.65% to 61.07%. Excessive BMI (overweight and obesity) increased from 27.09% to 29.50% in girls, and from 21.26% to 26.00% in boys. The mean percentage of FM was higher in girls than boys (23.17% vs. 16.20%, respectively). The mean FM decreased from 17.80% to 14.60% in boys and increased from 21.77% to 24.57% in girls. Poor nutritional behaviors were observed in 20.35% of children, more often in boys (22.25%) than in girls (18.50%). Between the initial and final assessments, an increase in the mean consumption of fruit, whole-grain bread, and milk was noted. These were products that should be consumed more often to demonstrate a healthy diet. However, the consumption of products that should be limited for a healthy diet, such as fried flour dishes, fried meat dishes, fatty cheeses, butter, fast food, sweets, and carbonated drinks, also increased. Boys more often than girls consumed red meat and poultry meat, eggs, butter, and fast food, while girls more often than boys consumed fruit, vegetables, yogurts, cottage cheese, wholemeal bread, fruit, and sweets. : Children usually showed moderate nutritional behavior. After four years, there was a significant increase in the consumption of fruit and whole-grain bread, i.e., products that should be consumed as part of a healthy diet, as well as fried flour and meat dishes, fatty cheeses, butter, fast food, and sweets, i.e., products whose consumption should be limited. With age, the percentage of children showing unfavorable nutritional behaviors and excessive body weight increased. More extreme levels of overweight and obesity and higher body fat contents were found in girls than boys. Although girls' nutritional behaviors were healthier, they were at a higher risk of excessive body weight. Increased promotion of a healthy diet and regular monitoring of body fat content in school-aged children is strongly recommended.