Do implementation intentions help to eat a healthy diet? A systematic review and meta-analysis of the empirical evidence.

Marieke A Adriaanse, Charlotte D W Vinkers, Denise T D De Ridder, Joop J Hox, John B F De Wit

Journal: Appetite 2011;56(1):183-93

PMID: 21056605

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Plain Language Summary

Eating a healthy diet reduces the likelihood of becoming overweight or chronically ill. Many people are aware of the health benefits of eating a healthy diet, and are hence motivated to eat healthily. This study is a review and meta-analysis with the aim to evaluate the effectiveness of setting implementation intentions (the where, when and how planning in goal setting) in promoting healthy eating behaviour. Results indicate that implementation intentions can be effective in increasing healthy eating behaviours with 12 studies showing an overall medium size effect on increasing fruit and vegetable consumption. Authors conclude that implementation intentions to promote healthy eating have more promising effects that those aiming to diminish unhealthy eating patterns.

Abstract

OBJECTIVE

This systematic review and meta-analysis examined whether implementation intentions are an effective tool to help people put their intentions to eat a healthy diet into practice. Additionally, it was investigated whether the quality of the outcome measures and the quality of the control conditions that are used in these studies influence implementation intentions' effectiveness.

METHODS

Twenty three empirical studies investigating the effect of implementation intentions on eating behavior were included. In assessing the empirical evidence, a distinction was made between studies that aim to increase healthy eating (i.e., eating more fruits) and studies that aim to diminish unhealthy eating (i.e., eating fewer unhealthy snacks).

RESULTS

Implementation intentions are an effective tool for promoting the inclusion of healthy food items in one's diet (Cohen's d=.51), but results for diminishing unhealthy eating patterns are less strong (Cohen's d=.29). For studies aiming to increase healthy eating, it was found that higher quality outcome measures and lower quality control conditions tended to yield stronger effects.

CONCLUSION

Implementation intentions are somewhat more effective in promoting healthy eating than in diminishing unhealthy eating, although for some studies promoting healthy eating effect sizes may have been inflated due to less than optimal control conditions.

Address: Department of Clinical & Health Psychology, Utrecht University, PO Box 80140, 3508 TC Utrecht, The Netherlands. [email protected]

DOI: 10.1016/j.appet.2010.10.012