Beyond intention: do specific plans increase health behaviours in patients in primary care? A study of fruit and vegetable consumption

https://doi.org/10.1016/j.socscimed.2004.10.014Get rights and content

Abstract

Increasing evidence suggests that implementation intentions are effective in moving people towards achieving health behaviour goals. However, the type of health behaviours for which they work best is unclear. Furthermore, implementation intentions appear to be less effective when studied in clinical rather than student populations. This prospective study tested implementation intentions with a complex, repeated health behaviour in a patient sample. A total of 120 cardiac patients in the UK were asked to increase their daily fruit and vegetable consumption by two portions and to maintain this over 3 months. Participants were randomly assigned to three groups (control, Theory of Planned Behaviour (TPB) questionnaire, TPB questionnaire+implementation intention) and telephoned at 7, 28 and 90 days follow-up to record daily consumption (24-h recall measure); 94 participants completed the study. Daily fruit and vegetable consumption increased from 2.88 portions (SD=1.67) at recruitment to 4.28 portions (SD=2.25) at 90 days. A 4×3 (time by group) mixed design ANCOVA was computed with daily fruit and vegetable consumption at recruitment entered as a covariate. This revealed a significant time effect (F (3, 270)=29.79, p<0.001) (η2=0.25) but non-significant group (F (2, 90)=0.32, p=0.73) (η2=0.07) and time by group effects (F (6, 270)=0.48, p=0.82) (η2=0.01). There was also a significant main effect of the covariate (F (1, 90)=48.51, p<0.001) (η2=0.35) and a significant time by covariate effect (F (3, 270)=12.14, p<0.001) (η2=0.12). Substantial increases in fruit and vegetable consumption were achieved particularly by participants who were eating low levels at recruitment. Consumption was not improved by implementation intentions. These findings are discussed in the context of the targeted health behaviour and sample.

Introduction

In order to promote positive health, public health practitioners must help overcome obstacles related to poverty, social exclusion, unemployment and poor housing (Department of Health (DOH), 1999). Health outcomes are also affected by individual behaviours. Indeed, individuals can contribute to their own health by adopting and maintaining health promoting behaviours (e.g. physical activity) and avoiding risk-associated health behaviours (e.g. smoking) (DOH, 1999).

Eating adequate amounts of fruit and vegetables on a daily basis is an important individual health promoting behaviour. It is currently recommended that people eat at least 400 g or five portions of fruit and vegetables each day in order to protect against coronary heart disease (CHD), stroke and cancers (Department of Health (1994), Department of Health (1998); US Department of Health and Human Services, 2004). This recommendation applies equally to healthy individuals and those with existing heart disease (DOH, 2000a). However, the current average UK daily consumption of fruit and vegetables is less than this recommended amount. On average men consume 2.7 portions per day and women consume 2.9 portions per day, with just 13% of males and 15% of females eating the recommended five portions per day (Henderson, Gregory, & Swan, 2002). These figures compare poorly to the US, where almost a quarter of the population eat at least five portions each day (National Center for Chronic Disease Prevention and Health Promotion, 2004). Furthermore, there are differences in consumption by income with households on lower incomes eating less (Hunt, Nichols, & Pryer, 2000; Steptoe et al., 2003).

The current UK government is committed to tackling this under-consumption of fruit and vegetables in the general population and cardiac patients (Department of Health (1999), Department of Health (2000a), Department of Health (2000b), Department of Health (2000c)). Standard Three of the National Service Framework for CHD (DOH, 2000a) requires general practitioners and primary care teams to collect data on the effectiveness of providing advice on diet to cardiac patients. Interventions to increase fruit and vegetable consumption in this clinical population are now a key priority, to obviate the need for statins which are often used to lower blood lipids, thus reducing the risks from high consumption of saturated fats (Hooper, 2001).

In order to promote positive health behaviours such as eating fruit and vegetables, the modifiable factors that predict this behaviour need to be identified. The Theory of Planned Behaviour (TPB; Ajzen, 1985) is a well-established social–cognitive model that has been used to further understanding of health behaviours (Armitage & Conner, 2001; Godin & Kok, 1996). The TPB states that the proximal determinant of behaviour is the intention to perform or to not perform that behaviour. Intention is determined by attitude towards the behaviour, subjective norm (perceptions of social pressure to perform the behaviour) and perceived behavioural control (PBC, perceptions of whether performing the behaviour is under the individual's control and the perceived ease or difficulty of performance). PBC can also influence behaviour directly in situations when it closely matches actual control. In general, the more positive one's attitude and subjective norm and the greater one's control, the more likely one is to form a strong intention and to perform the behaviour. There is empirical support for the theory across a broad range of behaviours. In a meta-analysis of 185 studies, the model accounted for 39% of the variance in intentions and 27% of the variance in behaviour (Armitage & Conner, 2001). In a review of 58 health behaviour studies, including addictive behaviours, healthy eating, physical activity, using condoms, clinical and screening behaviours, Godin and Kok (1996) found that on average the model explained 41% of the variance in intention and 34% of the variance in behaviour.

One of the criticisms of the TPB is that it explains high proportions of the variance in intentions, but is a weaker predictor of actual behaviour. This means that many people with positive intentions do not go on to perform the intended behaviour. Behavioural enaction models such as Gollwitzer's Implementation Intentions (Gollwitzer (1993), Gollwitzer (1996), Gollwitzer (1999)) address this limitation by distinguishing between the motivational and volitional stages of behavioural enaction. In the motivational stage outlined in the TPB, an individual forms a goal intention, i.e. makes the decision to perform a behaviour. In the subsequent volitional stage, the individual forms specific plans or implementation intentions that state exactly when, where and how the goal is to be achieved. Goal intentions take the form of ‘I intend to do X’, whereas implementation intentions specify ‘I intend to do X at time Y in place Z’. It is proposed that implementation intentions work by arranging for environmental cues to exert additional control over the behaviour enaction (Gollwitzer (1993), Gollwitzer (1999)). By specifying when and where the behaviour will be performed, the behaviour becomes linked to the environmental cue, which leads to the automatic elicitation of action when this cue is encountered.

Increasing evidence suggests that implementation intentions are effective in moving people towards achieving behavioural goals. Three meta-analyses have tested implementation intentions in achieving goals and performing behaviours (Gollwitzer & Sheeran, 2003; Koestner, Lekes, Powers, & Chicoine, 2002; Sheeran, 2002) and have reported medium effect sizes of 0.63, 0.54 and 0.70, respectively. In terms of health behaviours, a recent systematic review (Bridle, Steadman, & Jackson, 2004) found that implementation intentions alone (rather than implementation intentions plus a motivational intervention) significantly increased performance of health behaviours compared to controls in eight of the 14 studies reviewed. There were insufficient studies available to assess the types of health behaviours for which implementation intentions were effective. Indeed, from the research to date, it is unclear whether implementation intentions work better for single, one-off behaviours (e.g. attending cervical cancer screening, Sheeran & Orbell, 2000; Walsh, 2003; breast screening, Steadman, Rutter, & Quine, 2003; antenatal screening, Michie, Dormandy, & Marteau, in press) or repeated behaviours (e.g. breast self-examination, Orbell, Hodgkins & Sheeran, 1997; exercise, Milne, Orbell, & Sheeran, 2002; Prestwich, Lawton, & Conner, 2003; dental flossing, Lavin & Groarke, 2003). It is also uncertain whether they can be used more successfully for behaviours classified as simple (e.g. taking vitamin supplements, Quine, Rutter, & Steadman, 2004; Sheeran & Orbell, 1999) versus complex behaviours (e.g. booking and attending cervical cancer screening, Sheeran & Orbell, 2000; Walsh, 2003; exercise, Milne et al., 2002; Prestwich et al., 2003; healthy eating, Verplanken & Faes, 1999; eating fruit and vegetables, Kellar & Abraham, 2003).

This lack of conclusion suggests that more studies testing implementation intentions across different types of health behaviours (single versus repeated, simple versus complex) are required. Furthermore the length of time over which implementation intentions are most effective needs to be explored. To date only five studies have used a follow-up of longer than 1 month and three of these studies targeted behaviours that were performed just once in that time period (Sheeran & Orbell, 2000; Steadman et al., 2003; Walsh, 2003). Only two studies have looked at repeated behaviours over a longer time frame (Higgins & Conner, 2003; Orbell & Sheeran, 2000). This is an important gap in the research since many health behaviours need to be performed habitually and over the longer term to confer health benefits. This present research sought to extend the body of knowledge in this area. We tested implementation intentions with a repeated behaviour (increasing daily fruit and vegetable consumption) that was complex, requiring several necessary pre-conditions, such as having the fruit in the normal environment. Importantly, participants were followed up over three months.

A further issue that warrants investigation is the type of samples recruited to implementation intentions studies. In the meta-analysis by Sheeran (2002), stronger effects for implementation intentions were reported for student samples (r=+0.35) compared to non-student samples (r=+0.27). This moderation effect was not evident in the larger meta-analysis by Gollwitzer and Sheeran (2003). However, 10 of the 14 studies included in the systematic review of health behaviour studies (Bridle et al., 2004) were conducted with student samples and seven of these reported a significant effect for implementation intentions compared to just one of the four non-student sample studies. The review did not speculate on why implementation intentions appear to work better for students, although Michie et al. (in press) suggest that student samples may simply be more compliant than non-student samples. From a public health perspective, students are not representative of the groups of people that need to perform the targeted health behaviours. More research is needed to test whether implementation intentions work for patient and general population samples in promoting important health behaviours. The study reported here tested the efficacy of implementation intentions in promoting a health behaviour with a non-student sample. Participants were patients attending a secondary prevention CHD clinic in primary care.

This study tested whether implementation intentions could increase daily consumption of fruit and vegetables by two portions, in a sample of cardiac patients. No attempt was made to increase consumption to the recommended five portions a day as this is considered to be an unrealistic goal for many people who currently eat one portion a day. Furthermore, these individuals would benefit their health by simply working towards the recommended five portions (DOH, 2003a).

Section snippets

Participants and procedure

The study was approved by The Leeds Teaching Hospitals NHS Trust Local Research Ethics Committee. Participants were patients attending six secondary prevention CHD clinics in primary care in Leeds. Participants lived in two low-income areas of the city. These geographical areas had the smallest proportion of people eating the recommended five daily portions of fruit and vegetables, namely 16% and 20% compared to 23% in the city as a whole (Gent & Fear, 2003). Based on a small to medium effect

Participants

Of the 120 participants recruited to the study, five were removed from the sample as they represented outliers on the daily fruit and vegetable consumption measure. These outliers were identified using box plots and were consuming eight or nine portions of fruit and vegetables per day at recruitment.2 This left 115 participants at the outset of the study. Eleven participants were not contactable by the

Discussion and conclusions

The average daily fruit and vegetable consumption at recruitment for this sample was 2.88 portions. These figures were consistent with the UK national average of three portions a day (Henderson et al., 2002). Importantly, they indicated that there was scope for increasing consumption up to the recommended five portions a day. By 90 days follow-up, mean fruit and vegetable consumption for the whole sample had increased by 1.40 portions to 4.28 portions. This impressive increase was statistically

Acknowledgements

This research was funded by the former NHS Executive (Northern and Yorkshire) (reference number RRCC218LG). We would like to thank participating general practices for their help with recruitment. We are also grateful to the participants.

References (49)

  • B.B. Green et al.

    Effectiveness of telephone support in increasing physical activity levels in primary care patients

    American Journal of Preventive Medicine

    (2002)
  • I. Ajzen

    From intentions to actionsa theory of planned behavior

  • Ajzen, I. (2001). Construction of a standard questionnaire for the Theory of Planned Behavior. Retrieved August 25,...
  • C. Armitage et al.

    Efficacy of the Theory of Planned Behavioura meta-analytic review

    British Journal of Social Psychology

    (2001)
  • C. Bridle et al.

    A systematic review of the effectiveness of implementation intention interventions for health-related behaviours

    Proceedings of the British Psychological Society

    (2004)
  • Clifford, S., Barber, N., Horne, R., Elliott, R., & Hartley, E. (2003). Evaluation of a pharmacist-delivered...
  • D.N. Cox et al.

    Take five, a nutrition education intervention to increase fruit and vegetable intakesimpact on consumer choice and nutrient intakes

    British Journal of Nutrition

    (1998)
  • Nutritional aspects of cardiovascular disease. Report of the Cardiovascular Review Group, Committee on Medical Aspects of Food Policy

    (1994)
  • Nutritional aspects of the development of cancer. Report of the working group on diet and cancer of the Committee on Medical Aspects of Food and Nutrition Policy

    (1998)
  • Saving lives—our healthier nation

    (1999)
  • National service frameworkcoronary heart disease

    (2000)
  • The NHS plana plan for investment, a plan for reform

    (2000)
  • The NHS cancer plana plan for investment, a plan for reform

    (2000)
  • A local five-a-day initiativea handbook for delivery

    (2003)
  • Five-a-day community pilot initiativekey findings

    (2003)
  • M. Gent et al.

    Leeds lifestyle survey 2002

    (2003)
  • G. Godin et al.

    The theory of planned behaviora review of its applications to health-related behaviors

    The Science of Health Promotion

    (1996)
  • P.M. Gollwitzer

    The role of intentions

  • P.M. Gollwitzer

    The volitional benefits of planning

  • P.M. Gollwitzer

    Implementation intentionsstrong effects of simple plans

    American Psychologist

    (1999)
  • P.M. Gollwitzer et al.

    Implementation intentions and effective goal pursuit

    Journal of Personality and Social Psychology

    (1997)
  • Gollwitzer, P. M., & Sheeran, P. (2003). Bridging the intention–behaviour gap through strategic automization:...
  • Haddad, M., Inch, C., Glazier, R. H., Wilkins, A. L., Urbshott, G. B, Bayoumi, A., & Rourke, S. (2004). Patient support...
  • L. Henderson et al.

    The national diet and nutrition surveyadults aged 19 to 64 years

    (2002)
  • Cited by (0)

    View full text