Gardner, B. D., De Bruijn G. J., & Lally, P. (2011). A systematic review and meta-analysis of applications of the Self-Report Habit Index to nutrition and physical activity behaviors. Annual Behavior Medicine. 42(2), 174-187.

Abstract:
Background: Health behaviour models typically neglect habitual action. The Self-Report Habit Index (SRHI) permits synthesis of evidence of the influence of habit on behaviour.
Purpose: The purpose of this study is to review evidence around mean habit strength, habit-behaviour correlations, and habit x intention interactions, from applications of the SRHI to dietary, physical activity, and active travel behaviour.
Method: Electronic database searches identified 126 potentially relevant papers. Twenty-two papers (21 datasets) passed eligibility screening. Mean scores and correlations were meta-analysed using fixed, random and mixed effects, and interactions were synthesised via narrative review.
Results: Twenty-three habit-behaviour correlations and nine habit x intention interaction tests were found. Typical habit strength was located around the SRHI midpoint. Weighted habit-behaviour effects were medium-to-strong (fixed: r + = 0.44; random: r + = 0.46). Eight tests found that habit moderated the intention-behaviour relation.
Conclusion: More comprehensive understanding of nutrition and activity behaviours will be achieved by accounting for habitual responses to contextual cues.

 Link: http://www.ncbi.nlm.nih.gov/pubmed/21626256