The descriptive statistics and gender differences for all the study variables are presented in Table 1. Independent-sample t-tests showed that males scored significantly higher than females for LTPA, BMI, perceived physical ability, and subjective vitality. Females scored significantly higher than males on body dissatisfaction. Taking these results into account, subsequent analyses were performed separately by gender.

Table 1 Table 1 Descriptives and gender differences among the study variables Note

**p < 0.01; MET: metabolic equivalent; min: minutes.

Table 2 shows the bivariate Pearson correlations between the different variables. LTPA was significantly positively associated with physical ability and with subjective vitality in both males and females. Furthermore, in both genders, physical activity was not significantly related to BMI or body dissatisfaction. Body dissatisfaction and physical ability were significantly negatively associated with both genders. Furthermore, body dissatisfaction and BMI were significantly positively associated, whereas body dissatisfaction and subjective vitality were significantly negatively related in both genders. Finally, subjective vitality was positively and significantly associated with physical ability in both genders, whereas subjective vitality was negatively and significantly related to BMI in females but not in males.

Table 2 Table 2 Bivariate Pearson correlations between the study variables Note

Male correlations are located below the diagonal and female correlations are located above the diagonal.*p < 0.05; **p < 0.01

Initially, the hypothesized model fitted poorly to the data for both genders [males: χ² (5) = 31.25, p < 0.01; CFI = 0.85; NNFI = 0.49; RMSEA = 0.16 (90% CI = 0.11 - 0.22); SRMR = 0.10; and females: χ² (5) = 30.49, p < 0.01; CFI = 0.838; NNFI = 0.67; RMSEA = 0.131 (90% CI = 0.09 - 0.17); SRMR = 0.084]. The Modification Indices suggested adding a path from perceived physical ability and subjective vitality and following this the re-estimated model adequately fitted to the data from both males and females [males: χ² (4) = 8.12, p > 0.01; CFI = 0.98; NNFI = 0.92; RMSEA = 0.066 (90% CI = 0 - 0.15); SRMR = 0.033; and females: χ² (4) = 8.17, p > 0.01; CFI = 0.98; NNFI = 0.95; RMSEA = 0.059 (90% CI = 0 - 0.096); SRMR = 0.034]. The data obtained showed that physical activity levels positively predicted perceived physical ability in both genders (Figure 2). Body dissatisfaction was positively predicted by BMI and negatively predicted by perceived physical ability in both genders and perceived physical ability positively predicted subjective vitality in both genders. Lastly, body dissatisfaction acted as a negative predictor of subjective vitality in males and in females. The proposed model accounted for 36% of the variance of body dissatisfaction, 17% of the variance of subjective vitality in males; and 28% of the variance of body dissatisfaction and 10% of the variance of subjective vitality in females.

Figure 2

Note. All the coefficients are standardized. *p < 0.05; **p < 0.01; ♂: men; ♀: women.

The main objective of this study was to analyze the relationships between physical activity, body weight status, and perceived physical ability as antecedents of body dissatisfaction by testing them in a structural equation model, and then to assess their impact on psychological well-being. In this model, which was tested with young adults, similar associations were found between the study variables in both genders.

LTPA emerged as an antecedent that can influence body satisfaction, and consequently, psychological well-being, among young people. LTPA can improve perceptions of the physical ability which, on a practical level, suggests that levels of physical activity sufficient to allow positive experiences and the development of better perceptions of physical competence should be encouraged (Castillo & Molina-García, 2009; Castillo, Molina-García, & Álvarez, 2010). Future studies should specifically analyze the role of the context, such as the motivational climate and autonomous support where the physical activity occurs (Harwood, Keegan, Smith, & Raine, 2015), and the relationships between LTPA, the perception of physical ability, and body satisfaction.

The fact that the influence of perceived physical ability on body dissatisfaction was similar in men and women contrasts with the literature about adolescents (McCabe et al., 1991). From mid-adolescence, the athletic ability seems to be the main influence on body satisfaction among boys; however, girls are more specifically influenced by factors other than physical ability, such as social attitudes (Esnaola et al., 2010; Karr et al., 2013). It seems that, in young adulthood, both boys and girls can benefit from regular and satisfactory physical activity, which helps them to form a positive body image perception through positive evaluations of their physical ability. In other words, when young people perceive themselves as more athletically competent, they have more favorable attitudes towards their body image and they feel that they have more energy and vitality.

On the other hand, it is well known that regular LTPA among young adults is often associated with lower, and therefore healthier, body weights (Molina-Garcia et al., 2009; Molina-García et al., 2015; Provencher et al., 2009). In contrast, in the present study, the authors could not discern a significant relationship between LTPA and BMI, either men or women. Future longitudinal studies should, therefore, evaluate how potential weight gain during the 20s (Lewis et al., 2000), caused by decreases in LTPA, affects physical perceptions and psychological well-being.

Consistent with the present findings, another recent study conducted in a sample of 414 undergraduate students with a mean age of 22 years, showed that body image dissatisfaction mediated the association between BMI and health-related quality of life in men and women (Wilson et al., 2013). In the present study, university students with higher BMI were less satisfied with their body image compared to those with less body weight. These results help to clarify the relationships between body weight, body image, and mental health in young adults.

As evidence in the literature regarding adolescents has already shown (Lawler & Nixon, 2011), this study noted gender differences in the level of body dissatisfaction, with females showing greater dissatisfaction. In contrast, other studies suggest a reduction in, or the absence of, gender differences in body satisfaction among adult populations (Esnaola et al., 2010; Téllez Suárez et al., 2014). Perhaps these differences could be explained by differences in physical activity level between the genders, in favor of men. Lower levels of LTPA among women have been systematically reported in different studies looking at different age groups (Roman-Viñas et al., 2016). The present results justify the consideration of public health intervention programs that seek to improve the LTPA levels of the population, especially among women, in order to avoid body dissatisfaction and promote psychological well-being.

A relevant aspect of this study is that, in the female group, LTPA indirectly predicts lower body dissatisfaction and greater vitality. These results, which were not found in men, empirically confirm certain gender differences with regard to the effects of regular physical activity on body dissatisfaction and psychological well-being. They also highlight that the relationships between body dissatisfaction antecedents are complex and can be mediated by other variables. In this respect, understanding the mechanisms of the relationships between antecedents of body dissatisfaction and well-being can be very useful for public health research and the development of effective exercise programs. This is of particular interest among women because, as previously mentioned, they tend to be less physically active and also perceive themselves to be less physically competent (Castillo & Molina-García, 2009).

A limitation of this study is its transversal nature, which only allows us to talk about associations between variables and not cause-effect situations. However, although the structural equation models do not prove causation, they do suggest causal connections, and therefore, they are relevant to the current research as statistical analysis techniques. Another limitation is that the authors did not evaluate the eating habits of the university students participating in this study. Future studies on body dissatisfaction and psychological well-being should seek to integrate eating habit assessments, as well as physical activity evaluations, into the same analysis model, because eating variables have been associated with both body image perception and mental health (Ackard, Croll, & Kearney-Cooke, 2002). Finally, the use of a non-representative sample of university students limits the generalizability of the findings.

The present findings revealed similar associations between the model variables in both genders; BMI and perceived physical ability were significant antecedents of body dissatisfaction. These results support the inclusion of LTPA in intervention programs that seek to promote more satisfactory physical perceptions. In practice, an increase in physical activity levels would have a positive impact on improving body image satisfaction and can be considered an effective strategy for preventing the development of eating disorders and psychopathologies among young adults. In conclusion, the present findings suggest that body dissatisfaction may be a key target for psychological well-being interventions and programs.