School of Sport, Exercise and Health Sciences

Research

Project STIL

Sedentary Teenagers and Inactive Lifestyles

Funded by the British Heart Foundation, Health Education Board for Scotland, and Masterfoods Inc. (Stuart Biddle)

About the project

Project STIL (‘Sedentary Teenagers and Inactive Lifestyles’) was a project initially funded by the British Heart Foundation in 2001 [BHF Project Grant (PG/2000124)]. Additional funding was provided by the then Health Education Board for Scotland (HEBS) and Masterfoods.

The full project title was ‘Sedentary Behaviour in Young People: Prevalence and Determinants (PROJECT STIL)’.

Project STIL addressed three fundamental questions concerning sedentary behaviour in adolescent boys and girls in the UK:

  1. What is the prevalence of key sedentary behaviours in young people?
  2. What links exist between sedentary behaviours and other health-related behaviours?
  3. What are the main determinants of sedentary behaviour?

Research team

Principal Investigator: Professor Stuart Biddle

Co-grant holders:
Other project researchers:
  • Dr Trish Gorely
  • Dr Ian Murdey
  • Claire Mundy
  • Andrew Vince
  • Sarah Whitehead

Executive Summary of the Project

  • There is a great deal of concern about overweight and obesity in young people. Excessive weight gain during childhood and adolescence has been ‘blamed’ on sedentary lifestyles, particularly the use of electronic media such as television and computer games.

Project STIL

  • Project STIL (‘Sedentary Teenagers and Inactive Lifestyles’) at Loughborough University is a research programme that focuses on a wide range of sedentary and physically active behaviours. The current project had three main purposes: a) obtaining estimates for the prevalence of sedentary behaviour in youth, b) examining the links between sedentary behaviours and other health-related behaviours, and c) investigating factors associated with sedentary behaviour.
  • The key research questions were addressed using three methods: a) three systematic literature reviews, including one meta-analysis, b) a large cross-sectional study of prevalence and correlates of sedentary behaviour using a time-use diary method, and c) data from an 18-month longitudinal study of sedentary behaviour.
  • The reviews comprised a) a systematic review of prevalence, incidence and trends in youth sedentary behaviour, b) a systematic review of correlates of TV viewing in children and adolescents (Gorely, Marshall, & Biddle, 2004), and c) a meta-analysis of the relationships between TV viewing and computer game playing with body fatness and physical activity in young people (Marshall, Biddle, Gorely, Cameron, & Murdey, 2004).
  • Review-level data showed that TV viewing in children and youth is consistently and positively related to ethnicity (being non-white), body weight, between-meal snacking, parents’ TV viewing habits, weekend day, and having a TV in the bedroom.
  • Review-level data also showed that TV viewing in children and youth is consistently and negatively associated with parent income, parent education, and the number of parents living in the house.

Methods

  • The principal data collection instrument for the assessment of sedentary behaviour, in both the UK cross-sectional and longitudinal studies, was a self-report diary of “free-time” behaviours. School students completed the diary outside of school hours (3 weekdays and 1 weekend day). It asked the participants to write down what they were doing at 15-minute time intervals and participants also recorded where they were.  Demographic variables were also assessed.
  • In the longitudinal study, conducted in the East Midlands, England, measures were taken at baseline, 6 months,1 year, and 18 months. In addition to the diary, measures included pubertal status, height, weight, and body image.
  • For the cross-sectional UK study, assessment took place in 46 schools from 15 local education authorities in England, Northern Ireland, Scotland, and Wales. Data were collected in three phases: March-June and October-November 2002, September 2002-January 2003, and October-November 2003 with school Years 9-11 (ages 13-16 yrs). The final sample comprised 566 boys and 927 girls (total n=1493).

Prevalence and Patterns of Sedentary Behaviour

  • Review-level estimates showed young people watch an average of 2 hours 14 mins of TV per day, which decreases with age.
  • Review-level estimates showed that the majority (66%) of young people are ‘low’ users of TV (<2 hour.day-1), but 28% watch more than 4 hour.day-1. Watching more than 4 hours of TV per day during childhood is considered “excessive” by the American Academy of Pediatrics.
  • Review-level secular data suggest that the number of hours young people watch TV has probably not increased over the past 50 years.
  • Our national UK data showed that boys averaged 2hr and 6mins of TV viewing per day during the week and 3hr and 14mins at weekends; 49% watched up to 2 hours of TV per weekday with only a small minority (8%) exceeding 4 hour.day-1. This increased at weekends to 32% exceeding 4 hour.day-1. Boys in Year 9 watched more TV than those in Years 10 and 11.
  • Girls averaged 1hr and 41mins of TV viewing per day during the week and 2hr and 35mins at weekends; 62% watched up to 2 hours of TV per weekday with only a small minority (2%) exceeding 4 hour.day-1. This increased at weekends to 29% exceeding 4 hour.day-1. Girls in Year 9 watched more TV than those in Years 10 and 11.
  • During the week, boys averaged 24 min.day-1 playing computer games (52 minutes at weekends) and a further 18 min.day-1 using the computer for other purposes. 57% of boys reported no computer game playing on weekdays.
  • Girls averaged only 2 minutes (4 min at weekends) playing computer games and 13 minutes using the computer for other purposes.
  • Girls spent 46 min.day-1 in motorised transport during the week, and 56 min.day-1 at weekends. Boys reported similar use during the week (46 min.day-1) but slightly less than girls at weekends (42 min.day-1).  Only 15% of boys and 12% of girls reported no time in motorised transport during the week, whereas nearly one-third of boys (30%) and girls (35%) spent between 30 and 60 minutes daily in motorised transport.
  • Homework was a prevalent sedentary behaviour, with boys averaging 57 min.day-1 during the week and 41 at weekends, and girls 63 min.day-1 during the week and 43 at weekends.
  • During the week, boys (32 min.day-1) were markedly more active than girls (19 min.day-1) in sports and exercise. 46% of boys and 57% of girls reported no sports and exercise at all during the week, with figures rising to 48% and 66% at weekends, respectively. The least active in sports and exercise were Year 11 girls.
  • White Europeans spent more time in sports and exercise at weekend than other ethnicities.
  • Time in active transport averaged 22 min.day-1 during the week for boys and 23 min.day-1 for girls. 28% of boys and 22% of girls took no active transport during the week.
  • Results were minimally affected by socio-economic status.

Correlates of Sedentary Behaviour

  • Data from our meta-analysis and national sample showed relationships between TV viewing and physically active behaviours to be very small.
  • After school, there was a decline in the likelihood of motorised travel compared to before school, suggesting that children may rely more on motorised transport before school than after school. This also suggests that active travel may be possible for some children who use motorised means of travel to school.
  • Sport and exercise during the school week was most often reported in the early evening, watching TV was reported most often in the later evening. This suggests that the two behaviours may be able to co-exist to some extent.
  • There was never a time during the week when sports and exercise were more likely to occur than TV viewing, but at weekends the two behaviours occurred equally for boys during the day.
  • TV viewing was greater for those with TV sets in their bedroom than those without, and this appeared especially true for girls.
  • Longitudinal data showed that boys with more advanced pubertal status spent more time in sedentary behaviour during the week than their less mature counterparts.
  • Changes in sedentary behaviour were largely unrelated to changes in body image, except for girls during the week when greater sedentary behaviour was predicted by a change towards less positive body perceptions.
  • Physical activity was an inverse predictor of a cluster of sedentary behaviours, and the prediction was enhanced by accounting for the time young people spent outside. Interventions should focus on increasing opportunities for time outside of the house, requiring a mix of initiatives, ranging from structured activities, such as some sports, to environmental modifications based on attractiveness, accessibility, and safety.
  • While high and low TV viewing groups do differ in the amount of sports and exercise and time outside, the effect sizes are small-to-moderate.
  • When considering high and low sedentary groups, the amount of sports and exercise and time outside show much greater differences, revealing moderate and large effect sizes. This confirms our view that while TV viewing is a prevalent sedentary behaviour, it is a not a good marker of total sedentary behaviour. Interventions might be better targeted at a profile of several sedentary behaviours rather than TV alone, as well as time spent outside.
  • Using cluster analysis, diverse groupings across sedentary and active behaviours were found for both boys and girls. This suggests that no single sedentary behaviour is likely to be an effective intervention target for the majority of adolescents. In addition, the clusters confirmed that TV viewing and electronic media do not have to compete for time spent in sports and exercise.

Conclusions

  • Project STIL has provided comprehensive review-level and primary data on sedentary and physically active behaviours in youth. It shows that the widely-held assumption that popular electronic media (such as TV’s, computers, and computer games) are to blame for current trends in juvenile obesity is an over-simplification of a complex issue, and may even be wrong.
  • TV viewing is the most prevalent sedentary behaviour for young people but is only weakly related to physical activity and body fatness.
  • Most young people watch ‘acceptable’ amounts of TV each day (<2 hour.dy-1), but a significant minority watch what is considered by experts to be ‘excessive’ amounts.
  • TV viewing peaks in the later evening, a time when more active pursuits are less likely
  • If a reduction in TV viewing is desired, avoiding having a TV in the bedroom is a possible strategy, although our data suggest that the difference in TV viewing between those having a TV set in the bedroom and those who do not is small-to-moderate.
  • A better indication of sedentary behaviour is to assess various sedentary pursuits in combination. When this is done, young people engaging in high levels of sedentary behaviour do show clear tendencies to do less sport and exercise and spend less time outside. Time outside appears to be more powerful in accounting for sedentary behaviour than TV viewing per se and provides guidance for possible interventions.
  • No single sedentary behaviour can adequately account for the complex ways young people spend their free time.
  • Interventions to reduce sedentary behaviour and increase physical activity need to be multi-faceted and target those most in need of change.

For enquiries about these papers, please contact Stuart Biddle

The full project reports can be found here:

Pubications:

  • Atkin, A. J., Gorely, T., Biddle, S. J. H., Marshall, S. J., & Cameron, N. (2008). Critical hours: Physical activity and sedentary behavior of adolescents after school. Pediatric Exercise Science, 20, 446-456.
  • Biddle, S. J. H., Gorely, T., & Marshall, S. J. (2009). Is television viewing a suitable marker of sedentary behavior in young people? Annals of Behavioral Medicine, 38, 147-153.
  • Biddle, S. J. H., Gorely, T., Marshall, S. J., & Cameron, N. (2009). The prevalence of sedentary behavior and physical activity in leisure time: A study of Scottish adolescents using ecological momentary assessment. Preventive Medicine, 48(2), 151-155.
  • Biddle, S. J. H., Marshall, S. J., Gorely, T., & Cameron, N. (2009). Temporal and environmental patterns of sedentary and active behaviors during adolescents' leisure time. International Journal of Behavioral Medicine, 16(3), 278-286.
  • Gorely, T., Atkin, A., Biddle, S. J. H., & Marshall, S. J. (2009). Family circumstance, sedentary behaviour and physical activity in adolescents living in England: Project STIL. International Journal of Behavioral Nutrition and Physical Activity, 6(33), doi:10.1186/1479-5868-1186-1133.
  • Gorely, T., Biddle, S. J. H., Marshall, S. J., & Cameron, N. (2009). The prevalence of leisure time sedentary behaviour and physical activity in adolescent boys: An ecological momentary assessment approach. International Journal of Pediatric Obesity, 4(4), 289-298.
  • Gorely, T., Biddle, S. J. H., Marshall, S. J., Cameron, N., & Cassey, L. (2009). The association between distance to school, physical activity and sedentary behaviours in adolescents: Project STIL. Pediatric Exercise Science, 21, 450-461.
  • Gorely, T., Marshall, S. J., & Biddle, S. J. H. (2004). Couch kids: Correlates of television viewing among youth. International Journal of Behavioural Medicine, 11, 152-163.
  • Gorely, T., Marshall, S. J., Biddle, S. J. H., & Cameron, N. (2007a). Patterns of sedentary behaviour and physical activity among adolescents in the United Kingdom: Project STIL. Journal of Behavioral Medicine, 30(6), 521-531.
  • Gorely, T., Marshall, S. J., Biddle, S. J. H., & Cameron, N. (2007b). The prevalence of leisure time sedentary behaviour and physical activity in adolescent girls: An ecological momentary assessment approach. International Journal of Pediatric Obesity, 2(4), 227-234.
  • Marshall, S. J., Biddle, S. J. H., Gorely, T., Cameron, N., & Murdey, I. (2004). Relationships between media use, body fatness and physical activity in children and youth: A meta-analysis. International Journal of Obesity, 28, 1238-1246.
  • Marshall, S. J., Gorely, T., & Biddle, S. J. H. (2006). A descriptive epidemiology of screen-based media use in youth: A review and critique. Journal of Adolescence, 29(3), 333-349.
  • Murdey, I. D., Cameron, N., Biddle, S. J. H., Marshall, S. J., & Gorely, T. (2004). Pubertal development and sedentary behaviour during adolescence. Annals of Human Biology, 31, 75-86.
  • Murdey, I. D., Cameron, N., Biddle, S. J. H., Marshall, S. J., & Gorely, T. (2005). Short-term changes in sedentary behaviour during adolescence: Project STIL (Sedentary Teenagers and Inactive Lifestyles). Annals of Human Biology, 32, 283-296.