Environmental determinant: the family.

Many studies on family environmental influences have focused on the parent-child relationship and the influence of parental behaviors. Previous research demonstrated the important role of parents in the development of a healthy lifestyle in their children [11, 12]. Parents are gatekeepers of their children’s healthful eating and engagement in physical activities. Influencing factors include parenting practices such as modelling, monitoring, support, and encouragement [13–17] and more general concepts such as parenting styles [18–20]. However, inconsistent results regarding the influence of general parenting on children’s health behaviors have been reported [21, 22].

Other studies have examined more specific aspects of the family environment including media equipment, physical activity equipment, availability of healthful foods, and quantity and quality of family meals [23–28]. Although these studies emphasized the importance of the family environment for children’s and adolescents’ health behavior, the relationship between the different family environmental determinants and the underlying mechanisms of influence remain unclear [29, 30], and a theoretical framework is often missing. Furthermore, parental behaviors as well as specific environmental factors do not reflect the family as a whole [31].

The Model of Family Reciprocal Determinism: According to theoretical approaches such as Bandura’s Social Cognitive Theory, environmental and individual determinants are reciprocally interrelated and both affect health behavior [6]. The Model of Family Reciprocal Determinism extends the reciprocal determinism from the individual to the family and provides a framework for describing influences of the family environment on individual health behavior [32].

The family members live and interact in a shared family environment. Individuals as well as interactions between them affect the family environment, which in turn affects the individuals and their interactions. Hence, the ‘family-level’ extends beyond the individuals and their shared environment. The family can hence be considered a system [31]. According to the family systems approach, family is more than the sum of the individuals.

This theoretical framework implies reciprocal influences within and between individuals as well as between the individuals and the shared family environment. Hence, attributes of the family environment should affect individuals’ behavior and individual determinants. One relevant aspect of the family environment may be the Family Health Climate [33].

Family Health Climate: The Family Health Climate (FHC) is defined as the shared perceptions and cognitions concerning a healthy lifestyle within a family. It reflects the individual experience of daily family life, the evaluation of health-related topics and expectations with respect to typical values, behavior routines and interaction patterns within the family. The FHC serves as a framework for an individual’s everyday health behavior, is the basis of regulating health-related behaviors and provides references for valuing and interpreting individuals’ own behavior and that of others. Hence, the FHC is an aspect of the family environment that shapes everyday health behaviors of the family members. The FHC can be evaluated regarding healthy eating using the FHC-Nutrition scale and regarding physical activity using the FHC-Physical Activity scale. The FHC represents a family level variable that is intra- and inter-individually correlated to family environmental and to individual factors [33].

Previous research indicated that physical activity and dietary behavior are interrelated [34–38]. Because physical activity and eating take place within the family environment and are inherent parts of everyday family life, studying determinants of physical activity and dietary behavior simultaneously will be superior to studying these factors in isolation [39]. This allows examining the relationship between these two behavioral domains (see Fig 1, cross behavioral paths are presented by dotted lines). In particular, it enables testing for commonalities in form of shared variance and differences in form of unique variance.

In addition to environmental determinants of adolescent physical activity and eating behavior, individual’s motivation is well known to play a crucial role in the initiation and the maintenance of physical activity and healthful eating [40].

Individual determinant: intrinsic motivation.

Besides the quantity of motivation that predicts the engagement in different types of behaviors, it is also the ‘quality’ of motivation–intrinsic vs. extrinsic–that matters [41]. Previous studies have shown that autonomous motivation is an important predictor of initiating and maintaining healthful behaviors such as regular physical activity and a healthy diet. Intrinsically motivated behaviors are adopted because of interest and enjoyment [42] and thus are more likely to be maintained [43, 44]. Intrinsic motivation depends on the satisfaction of three basic psychological needs: autonomy, relatedness, and competence [41]. Individual’s motivation and the satisfaction of these basic needs are embedded in a social context. The social contexts affect need satisfaction by either facilitating or impairing the satisfaction of the basic needs and the development and maintenance of intrinsic motivation [42].

Hence, we hypothesized that the family environment affects adolescent’s intrinsic motivation [45], which in turn influences their health behaviors (Fig 1).

Family Health Climate, intrinsic motivation and health behavior.

The FHC is a family level variable reflecting an aspect of the shared family environment. Due to the reciprocal influences between the shared family environment and the individuals and their interactions, the FHC should be associated with individuals’ cognitive, motivational, and behavioral variables, with interactions related to physical activity or nutrition within the family, and with routines in family life. A positively evaluated FHC reflects that both being physically active and eating healthy is an important and integral part of everyday family life.

One of the core assumptions of the Self-Determination Theory is that children naturally tend to internalize attributes of the social context such as values, attitudes, and beliefs and to integrate them into a coherent sense of self [42, 45]. Therefore, it could be assumed that living in a family with a positive FHC is associated with autonomous motivation to be physically active and to choose healthful foods, which should be associated with more healthful behavior.

Demographics.

Mothers, fathers and adolescents completed questionnaires to obtain demographic information including age, gender, educational level and family structure. Age and gender were assessed by single questions. Adolescents stated which school they attended and which persons lived currently in the household (categories: ‘mother’, ‘father’, ‘siblings’, ‘grandmother’, ‘grandfather’ and ‘others’). Mothers and fathers stated their marital status, which was categorized into ‘living alone’ and ‘living in a partnership/marriage in the same household’ and ‘living in a partnership/marriage not in the same household’.

Parents’ educational level was assessed by asking for the highest school qualification. According to the German tripartite school system the categories ranged from ‘no qualification’ to ‘university-entrance diploma’. Employment status was categorized in ‘full-time’, ‘part-time’, ‘on parental leave’, ‘homemakers’, ‘unemployed’, ‘retired’, and ‘freelancer’.

Family Health Climate.

The Family Health Climate was assessed with the FHC-Scales for physical activity (FHC-PA) and for nutrition (FHC-NU) using a validated questionnaire [33]. The FHC-PA Scale consists of 14 items pertaining to three subscales (value, e.g. ‘In our family it is normal to be physically active in our leisure time’; cohesion, e.g. ‘…we have fun doing physical activities together (e.g. bike tours, hikes)’, and information, e.g. ‘…we collect information (e.g. on the internet) on physical activity and exercise’). The FHC-NU Scale comprises 17 items pertaining to four subscales (value, e.g. ‘…it is normal to choose healthful foods’, cohesion, e.g. ‘…we appreciate spending time together during meals’, communication, e.g. ‘…we talk about which foods are healthful’, and consensus, e.g. ‘…we rarely argue about food- or diet-related matters’). The items were rated on a 4-point Likert-type scale ranging from 0 = ‘not true’ to 3 = ‘true’. Scores representing the mean of all items were calculated for the FHC-PA and FHC-NU, respectively. Mothers, fathers and adolescents each completed the scales individually. The internal consistencies in this study were α_FHC-PA = .92 and α_FHC-NU = .86 for mothers, α_FHC-PA = .90 and α_FHC-NU = .86 for fathers, and α_FHC-PA = .90 and α_FHC-NU = .85 for adolescents. The Intra Class Correlations (ICC) were calculated to determine the agreement between the ratings of mothers, fathers and children. The ICC’s for FHC-PA were ICC (1,1) = .51 and ICC (1,3) = .75 and for FHC-NU ICC (1,1) = .29 and ICC (1,3) = .56. The overall FHC was calculated as the sum of the individual scores of child, mother and father (FHC_agg). The FHC_agg scores ranged between 0 and 9 and reflect the climate score within the family across its members [49].

Intrinsic motivation.

Adolescents’ intrinsic motivation of engaging in physical activities was measured by the subscale ‘intrinsic regulation’ of an adapted version of the Behavioural Regulation of Exercise Questionnaire 2 (BREQ-2) [50]. The subscale comprises four items (e.g. ‘I exercise because it’s fun’). The responses were scored on a 4-point Likert-type scale ranging from 0 = ‘not true’ to 3 = ‘true’. The internal consistencies in the current study were good (α = .90).

Adolescents’ intrinsic motivation of healthful eating was measured using an adapted version of the ‘intrinsic regulation’ subscale of the Regulation of Eating Behavior Scale (REBS) [51]. Item wording was modified to represent adolescents’ language and conditions of adolescents’ eating behavior. The focus of the items was changed to liking healthful meals and feeling good when eating healthful meals (four items: ‘I just like eating healthful meals’, ‘Eating healthful foods makes me feel good’, ‘I enjoy eating healthful food’, ‘I just feel good when I eat healthful food’). Responses were scored on the same 4-point Likert-type scale as described above, with a good internal consistency in this study (α = .87).

Both scales (BREQ-2, REBS) were translated and back-translated by a native speaker with excellent German skills and four German researchers with excellent English skills. Discrepancies were resolved through discussion.

Frequency of physical activity.

Adolescents completed two screening items to assess their habitual physical activity (60-minute MVPA screening measure) [52]. Corresponding to the guideline of the World Health Organization [53] the number of days with at least 60 minutes of moderate-to-vigorous physical activity during a ‘normal week’ and during the ‘last week’ were captured (‘In the past 7 days, on how many days were you physically active for a total of at least 60 minutes per day?’ and ‘In a typical or usual week, on how many days are you physically active for a total of at least 60 minutes per day?’). The 60-minutes MVPA screening measure is a brief, reliable and valid method for assessing adolescent physical activity [52]. Responses were scored on an 8-point scale ranging from 0 days to 7 days. According to the recommendations of the authors of the screening items, the mean of both scales was calculated [52].

Consumption of healthful foods.

To obtain information on the consumption of healthful foods, adolescents completed a Food Frequency Questionnaire [54]. The adolescents answered the question ‘How often do you normally eat the following foods?’ for 25 food items. Salad, vegetables and fruit represented healthful foods according to the recommendations ‘10 rules of healthful eating’ specified by the German Society of Nutrition [55]. The consumption of salad, vegetable and fruit was rated on a 7-point Likert-type scale (‘never’, ‘approximately one time per month’, ‘several times a month’, ‘approximately one time a week’, ‘several times a week’, ‘every day’, ‘several times a day’). The mean was calculated of the ratings of salad, vegetable and fruit, representing the consumption of healthful foods.

Mediating role of intrinsic motivation.

The FHC indirectly affected health behavior via adolescent’s motivation for both diet and physical activity. As intrinsic motivation is an individual determinant of long-term health enhancing behavior [43, 44], the relevance of linking family environmental and individual factors becomes evident. The results emphasize the relevance of the mediating role of intrinsic motivation for adolescent health behavior. Many cross-sectional and longitudinal studies have examined family or more precisely parental influences on children’s and adolescents’ health behavior [11]. Other studies have examined cognitive variables such as self-efficacy as mediators of parental behaviors [60, 61]. However, the role of individuals’ motivation as a mediating factor has rarely been considered [29].

Several studies [62–66] using the Self-Determination Theory (SDT) framework examined the role of a need-supportive social environment and evaluated the social environment mostly regarding need satisfaction from the children’s or adolescents’ point of view (mostly perceived autonomy support). This evaluation has been linked to autonomous motivation, cognitions (e.g. intentions, attitudes) and health behaviors (exercise, diet). The present study did not focus on the link between FHC and satisfaction of adolescent’s needs. Therefore, further studies should examine mechanisms underlying the association of FHC and intrinsic motivation, for instance, by considering the satisfaction of the needs for autonomy, relatedness, and competence. Although the mentioned studies did not focus on the role of autonomous motivation as a mediating factor between a family environmental factor and youth’s health behavior, their results indicated the relevance of considering this pathway.

Rutten, Boen and Seghers [67] investigated the role of children’s autonomous motivation as a mediator between environmental factors and pedometer-determined physical activity and found that children’s autonomous motivation (measured by the intrinsic and identified motivation subscales of the BREQ-2) [50] mediated the effect of children’s perceived exercise-related autonomy support and parental activity-related logistic support. Besides the study of Rutten et al. [67], few studies have linked parental behaviors (support, modelling etc.) or environmental factors (rules, availability of foods, family meals etc.) to SDT-based mediating factors. To the best of our knowledge there are no studies investigating the underlying mechanisms of family environmental factors in the nutritional context or integrating both health behaviors.

FHC and different health behaviors.

The results indicate that consumption of healthful foods and engagement in physical activities are differently affected by the family environment. While for physical activity only the indirect path via individual’s motivation was significant, adolescents’ dietary behavior was directly and indirectly affected by FHC-NU. The FHC-NU may be related to external factors that may have a direct impact on everyday food consumption such as the availability of specific foods [33], frequency of family meals [24] or specific rules [68].

Different motivational profiles may be useful for different behaviors such as physical activity and dietary behavior. Similarly to studying in the educational context, eating healthfully is not inherently enjoyable, especially for children and adolescents. Instead, healthful eating must be internalized within people’s broader goals and values. Therefore, the role of introjected, identified and integrated motivation should receive greater attention in this context [69].

Specific and general family environmental factors.

Previous studies investigated the clustering of physical activity and healthful eating on an individual behavioral level [37] and regarding parenting practices [70]. This study extended these previous findings to the environmental level shown by the assumed covariance between both specific climates. The covariance between the two specific FHCs suggests the existence of a higher level FHC. This general FHC–representing a general family environmental factor–is responsible for the clustering of physical activity and healthful dietary behavior.

The existence of a higher level FHC is in agreement with the finding of an apparent higher level intrinsic motivation. Intrinsic exercise motivation and intrinsic motivation for healthful eating shared unexplained variance. According to the hierarchical model of intrinsic and extrinsic motivation (HMIEM) [71], a higher level intrinsic motivation should be affected by higher level social factors suggesting that higher level intrinsic motivation may be affected by a general FHC. Moreover, the HMIEM states that the motivation at the contextual level (engagement in physical activity and healthful food choice) is affected by higher level motivation. For instance, Pelletier and Dion [72] have shown that general self-determination is positively associated with more autonomous regulation of eating behaviors and negatively associated with more controlled eating regulation. Furthermore, Mata et al. [38] showed that general self-determination as well as intrinsic exercise motivation predicted eating regulation. Beyond the interplay between different levels of motivation, motivation is also interrelated across different behaviors, which is in agreement with the residual covariance observed in our study.