Misperception and dissatisfaction of body size are common phenomena among adolescents . Since BSP and BSD can be determinants of health behaviors and unhealthy weight control practices, it is important to question whether or not adolescent girls who engage in PA interventions have a positive body image. In response to these concerns, this study aimed to examine the associations between health-related behaviors, BSP and BSD in girls who participated in a PA promotion intervention and to document the degree to which behaviors are associated with the expression of BSP or BSD. These findings suggest that some health-related behaviors, i.e. screen time, sleep patterns, are associated with overestimation and dissatisfaction, which may vary depending on weight control practices and weight status.
First, when compared by weight status subgroups the prevalence observed in a population of adolescents from the province of Quebec, FitSpirit participants living with OW/OB appeared to assess their weight status more accurately (10% vs. 42%, respectively) while the normal-weight subgroup underestimated their body size (13% vs. 41%, respectively) . These results are in line with Gesell et al. (2010), who found that a PA intervention among overweight children had an impact on the accuracy in body size perception, which could explain why girls living with OW/OB have a more accurate perception of their weight status . A review also demonstrated that the increase in the tendency to underestimate body size may be explained by the “visual normalization theory” . This theory suggests that one’s perception of his/her own body size depends on the size of the bodies this person is frequently exposed to in his/her environment . In the present study, the proportion of adolescents living with OW/OB was higher than in the one carried out in Quebec (23% vs. 19%, respectively) . Hence, in FitSpirit, the higher exposure to heavier bodies may explain the greater underestimation of body size among normal weight participants and the more accurate perception among those living with OW/OB. In addition, this difference in prevalence between the two studies could also be explained by a potential selection bias. Adolescents involved in FitSpirit desired to improve their level of PA for different reasons, including reasons related to BSD.
Moreover, our results are in line with previous studies showing that adolescents living with OW/OB report body size dissatisfaction more frequently . However, the present results revealed that girls living with OW/OB reported a higher proportion of the desire to reduce body size than another adolescent girl’s population from Quebec (92% vs. 78%, respectively) . This higher proportion could be explained by the context of the studies, including a possible selection bias induced by a higher interest toward PA in our study as well as a potential impact of the intervention itself. In addition, it has been shown that this type of intervention, exclusive to girls, could enhance the comparison of the body between the participants and may lead to a more frequent desire to reduce body size .
Regarding health behaviors, screen-time was positively associated with BSP and BSP. Thus, each hour of screen-time was associated with a significant increase of body size overestimation and a desire to reduce body size. Social media such as Instagram occupy an important proportion of screen-time in adolescents girls . The users of these social media platforms are frequently exposed to appearance-highlighting content, including retouched images, leading to unrealistic body ideals [40, 41]. Adolescent girls who fail to meet these standards may view their body concerns increase, which can be related to body size overestimation and dissatisfaction [7, 42, 43]. In line with the meta-analysis results, higher screen time may be associated with the desire to reduce body size .
Furthermore, research revealed that exposure to social media is linked to body dissatisfaction . Higher social media usage increases opportunities for adolescent users to engage in social comparisons as they can compare themselves to their friends, family, influencers and celebrities [45, 46]. A recent study by Scully et al. (2020) suggests that body dissatisfaction increases significantly with time spent on social comparisons . Furthermore, previous studies have shown that screen-time use can delay bedtime, reducing sleep duration in adolescents . Correspondingly, the present study results showed that one hour less of sleep was associated with a body size overestimation. Thus, a possible relationship could exist between screen-time, sleep duration, and overestimation of body size.
Even though PA did not emerge as an independent variable associated with body image, past studies showed that PA could be indirectly related via its association with screen-time and sleep duration. Greater screen-time has been associated with a lower PA  while a higher PA has improved sleep duration [50, 51]. In addition, because the current study is cross-section, it is impossible to establish a causal relationship. Considering that the data were collected towards the end of the FitSpirit intervention, the study participants are those who have remained engaged until this moment and therefore, are more inclined to achieve a minimum of PA, which could have impacted the results. Nevertheless, the results of the study suggest that 53% of the participants meet the daily 60 min of moderate-to-vigorous PA recommendation which is higher than what has been found in similar populations . Moreover, we do not have comparative data that would allow us to better analyze the impact of changes in PA on BSP and BSD during the FitSpirit intervention.
Another aim of the present study was to determine if the association between health behaviors with BSP and BSD differed by weight control practices. Results showed that fruit/vegetable consumption was associated with the underestimation of body size in those not trying to control their weight. We also found that PA was only associated with underestimation in the subgroup currently trying to control weight. This result is consistent with another study among primary school children that observed that girls who perceived themselves as overweight were favorable towards PA to control weight . Therefore, it is positive to note that PA level is not associated with BSP and BSD in the other weight control practices. Therefore, PA level is not related to body image variables in girls who are trying to lose weight or gain weight/muscles engaged in a PA promotion intervention.
Given that BSP and BSD are influenced by body weight status and weight control practices, understanding the association between these BSP and BSD by body weight status and weight control practice may provide a further understanding of these associations. Accordingly, as observed in Fig. 3, we found significant correlations between BSP and BSD scores according to weight control practices and weight status. A relationship was present in all normal-weight subgroups regardless of the weight control practices. As observed in Fig. 3A, the correlation is similar between the two weight subgroups. However, in Fig. 3D, the correlation is much stronger in adolescent girls living with OW/OB. The positioning suggests that the greater underestimation is associated with body size satisfaction with this group. This result is in line with the study by Bordeleau et al. (2021) conducted among primary school children, where an underestimation in children living with obesity was associated with a lower desire to be thinner .Thus, youth living with OW/OB who underestimate themselves protect themselves from a BSD and unhealthy weight control practices. Moreover, those who reported trying to control their weight seemed to be satisfied with their body size and almost all girls living with OW/OB were underestimators. As mentioned, PA was associated with BSP only in girls trying to control their weight. Considering that girls were assessed when they were already engaged in the intervention, they may have changed their habit towards PA which could have influenced their body size perception and satisfaction. Thus, although it is possible to note differences between perception and dissatisfaction by body weight status and weight control behaviors, studies are needed to further investigate their relationships and the association with health behaviors in longitudinal studies.
Strengths and limitations
The strengths of this study include the large number of participants and random selection process from the 240 participating schools. In addition, to our knowledge, no study evaluated the associations between BSP and BSD by weight control behaviors. Study limitations should also be considered when interpreting these findings. First, the cross-sectional design limits the analysis of temporal relationships between body image, health behaviors and weight control practices. Second, the intervention may have attracted girls interested in enhancing their PA level, which may not represent all adolescent girls. Fourth, FitSpirit is an intervention carried out by a school staff member with different levels of motivation , body image self-perceptions, and beliefs around weight control practices. Finally, self-reported measurements were used in our study. Previous studies suggest that self-reported height is often overestimated and weight underestimated among adolescent girls . This suggests that the BMI variable used this study might be lower than measured BMI. Adolescents also tend to self-report a higher level of PA  which could have impacted the results obtained in the association between PA and body image variables. Future research should consider the use of accelerometers to provide measures of PA.