Poor diet and physical inactivity are established risk factors for chronic disease. In young people, physical activity and healthy diets including regular breakfast consumption and adequate levels of fruit and vegetables, have important short- and long-term health protective effects. For example, physical activity in young people may benefit cardiovascular disease (CVD) risk factors, adiposity and bone health, which could influence health in adulthood 1. Child fruit and vegetable consumption has been associated with a lower incidence of respiratory symptoms 2 and appears to be protective against cancer in adulthood 3. Also, cross-sectional and longitudinal research has shown that young people who regularly eat breakfast are less likely to be overweight than those who skip breakfast 45. Despite such health benefits, young people are more likely to skip breakfast than any other meal 6 and data from the Health Behaviour in School-aged Children (HBSC) study shows that less than two-fifths of young people eat fruit daily, and only about a third eat vegetables daily 7. Also, recent data suggest that 30% of boys and 40% of girls in the United Kingdom (UK) do not meet the current physical activity guidelines 8. Health risks associated with individual behaviours are broadly acknowledged, yet, arguably a key issue for public health is that there is potential for synergistic effects of multiple health behaviours on the risk of chronic conditions and health outcomes 910. However, little is known about the relationship among these behaviours and their clustering patterns among adolescents in the UK.

There is evidence of an association between physical activity and dietary behaviours in adolescents. For example, Kremers et al. 11 and Driskell et al. 12 found an association between low fruit and vegetable consumption and low levels of physical activity. Keski-Rahkonen et al. 13 and Cohen et al. 14 found that breakfast skipping was associated with infrequent physical activity. Evidence for the clustering of two or more health behaviours in adolescents comes mainly from the US. Pronk et al. 15 found that only 31% of adolescents met the recommendations for adolescent-specific healthy lifestyle factor guidelines (including healthy weight, no smoking, physical activity and high quality diet). Sanchez et al. 16 found that nearly 80% of 11–15-year olds had multiple risk factors related to diet (fruit and vegetable consumption and calories from fat), physical activity and sedentary behaviour (TV time and moderate-to-vigorous-physical activity – MVPA). The tendency for physical activity and dietary behaviours to cluster has important implications for health promotion, highlighting the need for effective behaviour change interventions targeting multiple behaviours 12.

Targeting change in multiple behaviours offers the potential of increased health benefits, maximized health promotion, and reduced health care costs. Success in changing one or more lifestyle behaviour may also increase confidence or self-efficacy to improve risk behaviours that individuals have low motivation to change, and as such, health behaviour change may serve as a gateway to overall healthful lifestyle change 17. Given that adolescence is a critical period for the adoption of health behaviours, and that lifestyle habits and attitudes adopted during this life phase may track into adulthood 18, an improved understanding of health behaviour clustering among adolescents could identify high-risk groups and inform strategies for multiple health behaviour interventions.

Very few studies examining clustering of health behaviours among adolescents have used objective measures of physical activity 16, with studies usually relying on self-report methods. To our knowledge there is currently no published research examining whether breakfast consumption clusters with fruit and vegetable consumption and physical activity in a sample of adolescents from the UK. The current study aims to develop and add to the current literature by examining the prevalence and clustering patterns of multiple health behaviours among a sample of adolescents from the UK. This study will focus specifically on objectively assessed physical activity, plus fruit and vegetable consumption and breakfast consumption.

This study describes the prevalence and clustering patterns of three health behaviours (physical activity, fruit and vegetable consumption, breakfast consumption) in a sample of adolescents from the UK. Almost 54% of adolescents had multiple diet and physical activity risk behaviours, and only 6% achieved the recommendations for all three of the health behaviours. Findings highlight the need for effective strategies promoting multiple healthy lifestyle behaviours.

Higher levels of MVPA were found among boys, compared to girls, and in younger adolescents, compared to older adolescents. Such findings support previous research 2728 highlighting gender differences and age-related declines in physical activity, using objective measures of physical activity among adolescents. Recent research using accelerometry has also shown that age and gender differences are evident when comparing children as young as six and eleven years of age 2930. This suggests that the primary school years may be critical for the development of disparities in physical activity behaviours 31. Efforts to promote physical activity should begin in these critical years given that active children are more likely to become active adults 32. Promoting an active lifestyle to girls is challenging, and may require careful consideration of girls' activity preferences with a view to reassessing choices that are made available to them 33.

Consistent with previous research, adolescent girls ate breakfast on fewer days per week compared to boys 133435. Despite the evidence that adolescents who skip breakfast are more likely to be overweight than those who regularly eat breakfast 5, skipping breakfast may be a chosen method of weight control for girls, and in some individuals may be associated with dieting, or disordered eating 35. Further research is needed to understand the gender differences in breakfast consumption. Consuming a healthy breakfast on a daily basis should be promoted to young people with an emphasis on educating young girls about the negative health outcomes of breakfast skipping.

Older adolescents ate more fruit and vegetables per day, and were more likely to meet the recommendations for fruit and vegetable consumption, compared to younger adolescents. In contrast, review level evidence has shown a negative association between age and fruit and vegetable consumption 36. Contrasting findings may reflect a difference in the methodologies employed to assess fruit and vegetable consumption. Several studies have identified overestimation of fruit and vegetable intake when using food frequency questionnaires 3738. Although the YAQ is probably the most suitable and well-tested 1939 tool for assessing dietary intake among adolescents, there are problems assessing dietary intake with self-reported measures. Given that the fruit and vegetable consumption levels reported by participants in this study are higher than those reported by the same aged adolescents in the Health Survey for England 40, our findings may reflect an age-related response bias as well as an over-reporting by adolescents.

The most prevalent of the two-behaviour risk cluster included physical activity and fruit and vegetable consumption and supports previous evidence of such clustering 1116. Girls were more likely to have the two-behaviour risk cluster that paired physical activity and breakfast consumption. A possible explanation for such clustering is that adolescents who frequently skip breakfast have lower daily energy intakes, with higher daily energy intake being associated with more time spent being physically active 41. Girls who skip breakfast as part of a diet or method of weight control, may have less energy to be physically active. Efforts to promote both physical activity and regular breakfast consumption to adolescent girls, in particular, are needed. Consistent with previous research, girls had a higher number of risk factors related to physical activity and dietary behaviours compared to boys 16. Such findings provide additional evidence for support of gender specific interventions promoting physical activity and dietary behaviours.

Although health promotion programmes frequently target multiple behaviours, little is known about the best approaches to stimulating multiple behaviour change in adolescents 16. Reviews of multiple behaviour interventions with young people have revealed changes in some but not all behaviours, with significant effects more likely for dietary as opposed to physical activity outcomes 42. There is little evidence of covariation among diet and physical activity behaviours in adolescents over time 43. The implication is that multiple health behaviour change interventions may need to address health behaviours individually. Initial research comparing single (physical activity alone) versus multiple behaviour (physical activity and nutrition) interventions found that targeting two health behaviours was associated with less overall behaviour change, compared to targeting one behaviour 44. However, the intervention targeting both nutrition and physical activity was of low intensity and possibly not sufficient enough to increase fruit and vegetable consumption in the study population 44. Also, the efficacy of an intervention targeting fruit and vegetables alone was not assessed, so it is not known whether the lack of an effect for fruit and vegetable consumption was due to targeting multiple behaviours concurrently or to the consequence of trying to intervene on a difficult-to-change behaviour 44. Future research should investigate how best to achieve multiple health behaviour change in adolescent boys and girls.

The present study is innovative in that it examined the potential clustering patterns of breakfast consumption with fruit and vegetable consumption and objectively measured physical activity in a sample of adolescents from the UK. However, we acknowledge that there are a number of limitations that could be usefully addressed in future research. A limitation is the low response rate, reflecting difficulties in fostering compliance when using accelerometers with adolescents 45. Fruit and vegetable consumption levels reported by participants in this study were higher than the national averages for England, reflecting the difficulties in measuring diet in young people using self-report methods. Such high reported levels of fruit and vegetable consumption may also be reflective of our high SES sample. In the UK there are national differences in fruit and vegetable consumption according to SES, with higher levels of fruit and vegetables being consumed by those from higher SES groups 46. Staff at participating schools selected a subsample of classes to participate in the study in order to minimise disruption to the school timetable during data collection, this could have led to a selection bias. This study is also limited by its cross-sectional design and the generalisability of the results is limited because participants were predominantly White and of higher SES, thus findings should not be generalised beyond this population.

Many adolescents fail to meet multiple diet and physical activity recommendations, supporting previous evidence that physical activity and dietary behaviours do not occur in isolation. Differences in dietary and physical activity behaviours between adolescent boys and girls, as well as between older and younger adolescents, should be taken into consideration when assessing the efficacy of strategies promoting multiple health behaviour change.

The authors declare that they have no competing interests.

NP analyzed the data and conceived and drafted the original manuscript. AJA, SJHB, TG and CE provided critical feedback on drafts. All authors read and approved the final manuscript.