The utility of monetary contingency contracts for weight loss: a systematic review and meta-analysis

Abstract

Financial incentives to improve health have received increasing attention, but are subject to ethical concerns. Monetary Contingency Contracts (MCCs), which require individuals to deposit money that is refunded contingent on reaching a goal, are a potential alternative strategy. This review evaluates systematically the evidence for weight loss–related MCCs. Randomised controlled trials testing the effect of weight loss–related MCCs were identified in online databases. Random-effects meta-analyses were used to calculate overall effect sizes for weight loss and participant retention. The association between MCC characteristics and weight loss/participant retention effects was calculated using meta-regression. There was a significant small-to-medium effect of MCCs on weight loss during treatment when one outlier study was removed. Group refunds, deposit not paid as lump sum, participants setting their own deposit size and additional behaviour change techniques were associated with greater weight loss during treatment. Post-treatment, there was no significant effect of MCCs on weight loss. There was a significant small-to-medium effect of MCCs on participant retention during treatment. Researcher-set deposits paid as one lump sum, refunds delivered on an all-or-nothing basis and refunds contingent on attendance at classes were associated with greater retention during treatment. Post-treatment, there was no significant effect of MCCs on participant retention. The results support the use of MCCs to promote weight loss and participant retention up to the point that the incentive is removed and identifies the conditions under which MCCs work best.

Keywords:

• weight loss
• obesity
• incentives
• contracting

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental material

Supplemental material for this article can be accessed here: http://dx.doi.org/10.1080/17437199.2015.1030685

Notes

1. BCTs have been defined as ‘a systematic procedure included as an active component of an intervention designed to change behaviour’ (Michie & Johnston, 2013, p. 182). Examples include ‘self-monitoring of behavioural outcome’, whereby the person is asked to keep a record of measures expected to be influenced by the behaviour change (e.g., weight loss) and ‘provide instruction on how to perform the behaviour’, which involves telling the person how to perform a behaviour (see Michie et al. [2011] for full definitions). Recent acknowledgement of the need to standardise the reporting of the content of the behaviour change interventions has led to the development of taxonomies of BCTs used in healthy eating and physical activity interventions (Abraham & Michie, 2008; Michie et al., 2011, 2014). These taxonomies provide standardised definitions of BCTs used in such interventions ensuring people use the same labels for the same techniques. Such taxonomies have then been used in statistical reviews to identify which BCTs are most effective in various contexts (e.g., Dombrowski et al., 2012; Prestwich et al., 2014).

Additional information

Funding

This research was funded by the Institute of Psychological Sciences at the University of Leeds as part of a funded Ph.D. studentship.