The proportion of obese and overweight children is alarmingly high. This dictates the need for promoting healthy lifestyle and eating habits in children. Summer camps provide a wide range of activities to improve children’s health. However, methods used to assess children’s nutritional status during a camp session need to be analyzed in depth, and a rationale should be provided for the use of bioelectrical impedance analysis (BIA) and anthropometric measurements as efficacy criteria for summer camp healthcare. We examined 125 boys and 221 girls aged 8–15 years spending their summer holidays at 3 different camps. Measurements were taken twice: on days 1 and 2 upon arrival to a camp and 2 days before leaving for home. In each camp, both positive and negative health weight dynamics were observed. The overall weight dynamics in children from camps 1 and 2 were statistically insignificant (p = 0.415 and p = 0.585), in contrast to camp 3 where those changes were significant (p = 0.025). BIA revealed that less than 44.34% of children had gained skeletal muscle mass during their stay at the camp, whereas weight loss was associated with both decreased fat and skeletal muscle masses. BIA confirms the results of anthropometric measurements and also provides information about the diet offered to children and their level of physical activity. Therefore, the use of anthropometric measurements and BIA could be an informative method for assessing the efficacy of healthcare in summer camps.