The purpose of this study was to examine differences in socio-demographics and health behaviour between Belgian (European) first year university students who attended all final course exams and those who did not, as well as to identify weight and health behaviour related correlates of academic performance in those students who attended all course exams. Results indicated that female students showed higher GPA’s in the first year at university. Furthermore, increases in (over) weight over the first semester, sedentary behaviours, unhealthy eating and drinking behaviours negatively predicted academic performance.
In agreement with findings of previous US studies [3, 6, 7, 21], female college or university students tended to have higher grades than male students. This could be partly explained by the fact that women more often show motivation, discipline and time management skills that are important to perform well in higher education [28, 29]. Moreover, the study of Sheard et al.  revealed that female university students also reported a significantly higher mean score on commitment compared to male students, whilst commitment was the most important positive correlate of academic grades. The latter increases the likelihood of female university students achieving higher grades than their male counterparts . Furthermore, we observed the same trend when comparing students who attended all course exams with those who did not, i.e. the majority of students who did not attend all course exams during the first year at university were male. Similar to previous findings in the literature [4–6] GPA in the last year of secondary school predicted first year university GPA positively.
Increases in weight, BMI and WC over the first semester period were related to lower academic performance. Additionally, students who did not attend all course exams during the first year of university showed a significantly higher increase in WC during the first semester than those who attended all final course exams. Since no literature on this matter was available, no comparison could be made. However, these results indicated that increases in weight, BMI and WC may have affected students’ cognitive performances. It might also be that students who lacked discipline to maintain weight were equally not disciplined to perform well academically. Furthermore, it has been shown that medically defined overweight status is negatively associated with academic achievement [30, 31].
Similar to other studies conducted in US university students [3, 4], our results indicated that physical activity was not related to academic performance. This finding is in contrast with the review study of Singh et al.  relating physical activity with academic performance in children and adolescents. This latter study found strong evidence of a significant positive relationship between physical activity and academic performance. According to Hillman et al.  regular participation in physical activity is linked to enhancement of brain function and cognition, and thus positively influencing academic performance. In Singh et al. , several hypothesized physiological mechanisms (e.g. increased blood and oxygen flow to the brain and increased levels of endocrine processes) explaining the beneficial effect of exercise on cognition are given. In addition, regular participation in sport activities may improve students’ classroom behaviour and concentration during the lessons . Therefore, we could expect that students who were more engaged in physical activities would perform better academically. However, on the other hand, when spending more time exercising, students possibly tended to spend less time on their academic work, so this might have offset the beneficial effects of physical activity on GPA at university.
Regarding sedentary behaviour, gaming on weekdays negatively predicted GPA. In addition, computer activities on weekend days showed a trend towards significance (p < 0.1). This suggests a negative influence of ‘screen activities’ on grade points in university students. Earlier research showed that the amount of time a university student spends playing video games is negatively related with GPA . Similar to physical activity, this negative relationship might be explained by the fact that university students who spent more time playing videogames tended to spend less time studying. However, in this study, the amount of reading (incl. leisure time reading) and studying during the whole week did not correlate significantly with GPA. In contrast to the literature , the amount of sleep was not associated with academic performance.
Students who were on a diet, ate more in the student restaurant, consumed more (sugar containing or diet) sodas or ate French fries more frequently tended to have lower GPA’s. Similar results have been found in adolescents showing that unhealthy food choices (including fast foods) were negatively related, whereas fruit and vegetable consumption was positively related to secondary school end-of-year achievement [13, 15]. In addition, Florence et al.  concluded that 10 year old students with decreased overall diet quality were more likely to perform poorly on an assessment used as a measure for academic performance. Moreover, dietary adequacy, variety, fruit and vegetable consumption and dietary fat intake were demonstrated as being important to academic performance . Concerning the association between GPA and eating at the student restaurant, it could be that university students tend to make more unhealthy choices (e.g. more fatty foods and less fruit and vegetables) when eating in the campus restaurant. When controlled for other significant variables, being on a diet remained significant in the multivariate model. No previous correlational studies have assessed dieting status so far. These results suggest that unhealthy eating behaviours are related to lower academic performance.
Finally, even when controlled for other significant variables, frequency of alcohol use was associated with academic performance. The more frequent students drank alcohol, the lower their academic grades at the end of their first year at university. The latter confirmed the findings of Singleton et al.  showing a similar negative correlation between alcohol consumption and GPA in US university students. Furthermore, in a Belgian study, a 25% excess risk of failing at university was found in first year students who met alcohol dependence criteria .
According to our results many weight and health-related behaviours were associated with university students’ academic performance, with dieting status and alcohol use emerging as the strongest correlates of academic performance, once controlled for other significant variables. However, we should be careful interpreting these results. In a review and meta-analysis of Richardson et al. , several psychological correlates of university students’ academic performance were reported. Self-esteem, academic intrinsic motivation, and academic and performance self-efficacy were positively associated with GPA . Goal commitment and social support showed a positive relation with GPA, whereas measures of psychological health (general and academic stress) were negatively correlated with academic achievement . In addition, Chambel et al.  indicated that higher levels of academic satisfaction  influence student performance positively. Taking this into account, underlying psychological/motivational mechanisms might be mediating or confounding these relationships. Typically, a mediator is a third variable affecting the relation between two other variables . E.g. previous research of Kristjansson et al. [14, 15] in secondary school adolescents indicated a weak mediating role of both self-esteem and school contentment (satisfaction) on the relation between health behaviours and academic grades. A confounder, on the other hand, causes both the independent and the dependent variable . It might also be that students who were more disciplined concerning their health behaviour, showed the same discipline regarding academic performance. E.g. lack of self-discipline might cause students to eat more unhealthy foods, and at the same time, it might cause these students to perform worse academically. A study of Duckworth et al.  showed that self-discipline accounted for more than twice as much variance as IQ in final grades in adolescents. Therefore, future studies should investigate possible mediation and/or confounder effects of psychological/motivational aspects on the relation between health behaviour and academic performance in university students.
A first strength of this study is that we were able to regress academic performance onto objectively measured first semester changes in weight, BMI, fat% and WC. Secondly, in contrast to other studies, we used objective GPA’s (obtained from official university records) instead of self-reports. However, this study has some limitations as well. Firstly, it should be mentioned that no information was collected to verify whether those who did not carry through did so for academic reasons, or reasons related to health. Therefore, it might be that students who did not attend all course exams did not automatically lack self-discipline or academic competences, but were forced to miss out on exams due to health related reasons. Secondly, since our health-related questionnaire was only completed at follow-up, we were not able to regress academic performance onto changes in physical activity, dietary habits, and other health behaviours over time. Thirdly, because of the limited sample size (n = 42) we chose to exclude secondary school GPA from the t-tests as well as from the multivariate regression model to ensure sufficient degrees of freedom. Subsequently, we did not control our multivariate regression model for secondary school GPA. Fourthly, we have to be aware that the use of objective measures of physical activity (e.g. accelerometers) and food frequency questionnaires or food diaries would have given us more accurate and detailed information on physical activity and dietary behaviour. Finally, due to a relatively small sample size with a slightly different mean age and gender distribution in comparison to all freshmen, we have to be cautious with generalizing these results to the entire student population.