Research has explored the interplay between eating and movement behaviors, considering their potential interactional nature (i.e., changes in one domain may aggregate with changes in others) (36, 37), and that health-enhancing spill-over effects may arise when being more physically active and having a healthier eating pattern co-occur (10, 38), suggesting a pattern of protective versus deleterious associations (31). However, contrarily to the wealth of evidence concerning the protective role of overall PA in this regard, limited research is available on the relationship between SB specific domains and eating-related indicators. Thus, this study sought to analyze the associations between distinct SB related domains (i.e., work, leisure-time, and transport) and several eating-related markers (i.e., food intake, protective eating habits profile, and eating behavior indicators) in adults.
Overall, findings extend the ones from previous studies focusing on PA and reporting a reduced preference for processed foods, red meat, fried foods, soft drinks, and snacking in more physically active individuals (6). We found that SB, more specifically leisure-time SB, was consistently and negatively associated with fruits, vegetables, and fish consumption, use of olive oil, and breakfast consumption; and positively associated with fast-food consumption, red meat, and meal skipping, irrespective of sex, BMI category, and PA level. However, some of these results disappeared when adjusting for age, which means that these associations somehow vary with age. We could not find any significant associations between work-related SB and eating-related indicators; future investigations are needed to confirm these findings.
In line with previous evidence showing that lifestyle PA is positively associated with several eating behavior indicators (8, 9), results showed that leisure-time and transport related SB - but not work-related SB - also seem to be associated with these outcomes. Transport-related SB was negatively associated with cognitive eating restraint, a potential risk factor for the adoption of dysfunctional eating patterns (39, 40). Thus, these findings extend the ones from a systematic review that found SB to be associated with elements of a less healthier diet including lower fruit and vegetable consumption, higher consumption of energy-dense snacks, drinks, fast food, and a higher total energy intake (17). Still, according to our findings, not all SB domains appear to be related with a less healthy diet. Future studies must confirm these results.
One investigation including participants from five urban regions in Europe found that domain-specific SBs were related to unhealthy dietary behaviors, except for transport related SB (24). Our results do not align with these findings, as a higher transport-related SB was associated with a lower adherence to the Mediterranean diet (e.g., lower intake of fruits and vegetables, and lower use of olive oil), but also with a less protective eating profile, including lower breakfast consumption and higher fast-food consumption. Furthermore, after the adjustment for sex, BMI, and PA level, similar results were obtained, meaning that the associations were independent from these variables.
Regarding eating behavior indicators, transport-related SB was associated with lower cognitive eating restraint (i.e., tendency to restrict food intake to manage weight (41)), although these associations seem to depend on people’s BMI. One possible explanation for these findings might be related to the high percentage of our sample that commuted to and from work by using public transportation (approximately 45%). This type of transportation has been associated with greater steps and MVPA when compared to private transportation (42, 43). It might just be that those using public transportation feel less demanded to control their eating, especially if they are not overweight, due to their potential higher PA level. On the other hand, we can speculate that transport-related SB may boost screen time during this period, resulting in a decreased cognitive impulse control and subsequent increase in brain activation for high energy dense foods, thus possibly contributing to a disinhibited vs. restricted eating pattern (23). Screen time has also been associated with lower vegetables and fruits intake (20).
Work-related SB was not associated with any eating indicator, highlighting that the deleterious role of SB may not only be related to SB itself (physiologically), but with participants’ global health behavior profile. When considering other outcomes (e.g., mental health), this different pattern of associations by domain has also been observed. For example, leisure-time SB, characterized as mentally passive (e.g., watching TV), was found to increase the risk of depression in adults, while there was no harm associated with mentally active SB (e.g., using the computer at work/school) (44), therefore suggesting that not only the domain can play a role in the association between SB and mental health, as the specific type of SB within the domain may be of relevance. It may be the case that when leisure-time is not fulfilled with activities that nurture both body and mind, that may be a marker for risky health behaviors, such as a high sedentary time not occupied with any intentional activity triggering dysfunctional eating patterns and behaviors.
Indeed, excessive time in SB has been shown to be independently associated with several non-communicable diseases (14, 15), and even with higher mortality (14, 16). Hence, there is a possibility that SB may play a specific role in people’s diet and eating behaviors, that can somehow alter the association between PA and these important outcomes (e.g., by limiting PA’s health-related outcomes). Future research would do well to explore these interactions.
Despite our focus on SB, we also explored the associations between PA and eating-related indicators and confirmed previous findings showing that higher PA levels were positively associated with healthier dietary choices (45), therefore reinforcing PA’s role as a gateway behavior for healthier eating. Unexpectedly, PA levels were not associated with any eating behavior indicator in the overall sample, but after controlling for age, a positive association with eating for physical rather than emotional reasons emerged. This finding is in line with previous studies, reporting negative associations between PA and emotional eating (8, 9), further suggesting that age might be a relevant factor in this relationship. Post-hoc analysis, exploring these associations by age tercile, showed that PA was associated with higher intuitive eating (i.e., in response to physiological hunger and satiety signals and not driven by emotional reasons) only in the older participants (3rd tercile). In other words, age appears to be a protective factor against more emotional (less healthy) eating pattern.
In today’s obesogenic food environment, regulating eating behavior is very demanding, with homeostatic drives involved in appetite control being easily superseded by hedonic, reward-based drives, that encourage eating beyond physiological necessity (46). Also, emotional states have an important impact over one’s eating behavior, mainly by depleting his/her cognitive resources (47), which has in fact been associated with increased consumption of unhealthy, highly palatable foods (48). In this context, the quality of food choices is determined by food hedonics, and deliberately and successfully resisting external and internal eating cues requires the identification of factors that can facilitate one’s eating self-regulation. SB, as PA, could be such a factor.
This study’s data was cross-sectional, and therefore the direction of relationships analysed cannot be clarified. The study only aimed at exploring the interplay amongst the variables, thus, causality cannot be inferred. Another limitation concerns the use of a self-report survey to measure the variables under scrutiny, thus, potential bias, such as social desirability, cannot be excluded. In the domain of eating-related indicators, an adapted self-report set of questions was also created, following previous studies and what has been advocated to conduct studies pertaining to a behavioral epidemiology framework (31, 49). Furthermore, although device-based measures, to assess PA and SB, would be preferred due to their accuracy, these types of devices may not capture domain and context specific behaviors, essential for this study’s aims. Thus, according to best practices, the survey was based on widely used, validated methods to measure PA and SB. There was an effort in balancing the need for precision vs. feasibility.
The main analyses conducted in this study allowed us to explore the cross-sectional associations between distinct SB domains (i.e., work, leisure-time, and transport) and several eating-related markers (i.e., food intake, eating habits’ protective profile, and eating behavior indicators) in adults, while also exploring if these relationships are independent of sex, age, BMI, and PA levels. This was an underexplored research arena as very limited research addressing the associations between SB domains and eating is available, neglecting the potentially interactive effects of multiple diet components and related behaviors.
Taken together, our results highlight the importance of considering the complexity embedded in health behaviors. Sedentary behaviors should not only be considered in terms of their physiological impact. The potential health risk of this type of behavior lies on the behavioral health patterns involved and their psychological consequences. SB domains are, thus, of critical importance, also for eating behavior regulation, as demonstrated in other outcomes (e.g., mental health) (50). Health literacy and public health campaigns devoted to promoting more active and healthier lifestyles may benefit from these findings- targeting SB domains of higher risk (i.e., leisure-time, and transport to some extent).