Although dietary supplement use is increasing in Europe and the USA, little research involving adults’ beliefs regarding dietary supplements has been conducted. Therefore, the present study aimed to explore and compare users’ and non-users’ beliefs towards dietary supplements.

Thirteen focus group discussions were conducted of which seven groups were dietary supplement users and six groups were non-users. Based on the socio-cognitive factors of the Integrated Change Model, a semi-structured topic guide was set up. The discussions were audio-recorded and subjected to qualitative content analysis, applying the framework approach.

Data were collected in Maastricht, the Netherlands, in 2014 and 2015.

In total fifty-six individuals participated in the study, of whom twenty-eight were dietary supplement users and twenty-eight non-users. The average age of participants was 42·9 years.

Dietary supplement users’ attitude beliefs were mainly related to mental and physical health enhancement, illness prevention and curative health benefits. Users were critical of the nutritional knowledge of health professionals and of the quality of food products. Non-users were convinced that the human body does not need any support and that regular food is enough to cover one’s nutritional needs. Users and non-users held comparable beliefs regarding the definition and risks of dietary supplements, and perceived social influences.

In their decision about dietary supplement use, both groups were guided by their own convictions to a great extent. Both groups would benefit from improved understanding of the health effects of dietary supplements to improve informed decision making.

To explore the influences of migration to a Western country on obesity and related risk factors by comparing measures of body composition and energy balance-related behaviours between Turkish adolescents in Turkey (TR-TR) and adolescents from Turkish immigrant ethnicity in the Netherlands (TR-NL).

Cross-sectional survey or baseline intervention data from six Dutch school-based studies and one Turkish study.

Primary and secondary schools.

A total of 915 (49 % girls; mean age 13·1 (sd 0·8) years) TR-TR adolescents and 433 (51 % girls; mean age 11·7 (sd 1·3) years) TR-NL adolescents were included. Outcome measures were self-reported sugar-containing beverage consumption, fruit and vegetable intake, screen time, physical activity, measured body height and weight, BMI, waist and hip circumferences, and skinfold thicknesses.

Our data showed that more TR-NL adolescents were overweight (31 % v. 26 %) and obese (9 % v. 6 %) and had significantly higher mean BMI (21·1 v. 20·0 kg/m2), waist circumference (72·2 v. 71·3 cm) and suprailiac skinfold thickness (19·8 v. 13·1 mm) than TR-TR adolescents. TR-NL adolescents reported significantly higher sugar-containing beverage consumption (1173 v. 115 ml/d), less fruit and vegetable intake (295 v. 647 g/d), less screen time (253 v. 467 min/d) and higher physical activity levels (61 v. 27 min/d) than TR-TR adolescents.

Immigrant adolescents in the Netherlands were more often overweight and had a less favourable dietary pattern than their peers in Turkey, while their physical activity and screen time patterns were more favourable. These results suggest that adolescents from Turkish immigrant ethnicity in the Netherlands have adopted lifestyles towards the host culture.

To examine cross-sectional and longitudinal (one-year follow-up) associations of parental feeding styles with child snacking behaviour and weight in the context of general parenting, taking into account the multidimensionality of the controlling feeding style.

Linear regression analyses were performed. Parents completed a questionnaire to measure five feeding style dimensions (Instrumental Feeding, Emotional Feeding, Encouragement, Overt Control and Covert Control) and children's fruit, energy-dense snack and sugar-sweetened beverage (SSB) intakes. Children's height and weight were measured to calculate their BMI Z-scores. Moderation by parenting style was tested by adding interaction terms to the regression analyses.

Observational study in the Netherlands.

Parent–child dyads (n 1275) participating in the INPACT (IVO Nutrition and Physical Activity Child cohorT) study; children were (on average) 9 years of age.

Instrumental Feeding and Emotional Feeding were negatively related to child fruit intake one year later and positively to (changes in) child energy-dense snack intake. Encouragement was negatively related to child energy-dense snacking and SSB intake one year later. Overt Control was cross-sectionally and prospectively related to (changes in) child energy-dense snacking and SSB intake in a negative direction. Covert Control showed similar associations with child energy-dense snacking and SSB intake as Overt Control. Although Covert Control was also positively related to child fruit intake and (changes in) child BMI Z-score, bootstrapping analyses revealed only a differential effect of Overt Control and Covert Control on child BMI Z-score one year later, with Covert Control displaying a stronger, positive association. Moderation analyses showed that some significant associations between parental feeding styles and outcome measures were dependent on the degree of psychological control and behavioural control.

Instrumental Feeding and Emotional Feeding may have a detrimental impact on children's snacking behaviour, while Encouragement, Overt Control and Covert Control may lead to less energy-dense snacking and less SSB intake. Overt Control and Covert Control have differential effects on child BMI Z-score one year later, which supports the idea that they should be treated as separate constructs. Prospective studies with a longer follow-up may elucidate the causal pathways between the various feeding styles and children's snacking behaviour and weight, as well as the moderating influences of psychological and behavioural control.

To explore whether the effects on dietary behaviours of a computer-tailored intervention aimed to prevent excessive weight gain among adolescents, FATaintPHAT, were moderated by sociodemographic, cognitive and home environmental factors.

A two-group cluster randomized trial. Potential moderation of the outcome measures (consumption of sugar-sweetened beverages, snacks, fruits and vegetables) was studied by gender, education level, ethnicity, awareness of risk behaviour, intention and home availability.

Twenty schools in the Netherlands.

Students (n 883) aged 12–13 years.

Of the twenty-four interactions tested, only three were significant. The intervention effect on sugar-sweetened beverages was moderated by level of education (P = 0·009); intervention effects were found only among academic preparatory students. The intervention effects on fruit and vegetable intake were moderated by awareness of fruit intake (P < 0·001) and home availability of vegetables (P = 0·007); an effect on fruit intake was found only among students who were aware of their low fruit intake at baseline and an effect on vegetable consumption was found only among students who reported that vegetables were always available at their home.

The effects of the intervention generally did not differ between sociodemographic subgroups. The moderation by home availability illustrates that the environment may influence the effects of educational interventions.

To examine the associations of perceived physical environmental factors (availability of physical activity (PA) attributes at home, PA facilities in the neighbourhood, neighbourhood pleasantness and safety) and social environmental factors (parental sports behaviour and parental rule regarding sports participation) with adolescent leisure-time sports participation, and to explore whether the associations found were mediated by individual cognitions as derived from the theory of planned behaviour (TPB).

Cross-sectional study.

In schoolyear 2005/2006 adolescents from seventeen schools in Rotterdam, the Netherlands, completed a questionnaire during school hours that included self-reported measures of leisure-time sports participation, perceived physical environmental factors and TPB variables. Information about parental sports behaviour and parental rule was obtained from a questionnaire that was completed by one parent of the adolescents.

Data were collected from 584 adolescent–parent combinations.

Data were analysed with multi-level logistic regression analyses. Availability of PA attributes at home (OR = 1·26), parents’ sports behaviour (OR = 2·03) and parental rule (OR = 1·64) were associated with a higher likelihood of adolescents’ leisure-time sports participation. These associations were partly mediated by attitude and intention.

Adolescents were more likely to engage in leisure-time sports when PA attributes were available at home, when parents participated in sports activities and had a rule about their offspring participation in sports activities. These associations were partly mediated by attitude and intention. These results suggest that parents can importantly promote sports participation among their offspring by making sports activities accessible and a family routine.