Self-efficacy, habit strength, health locus of control and response to the personalised nutrition Food4Me intervention study

Purpose: Randomised controlled trials identify causal links between variables but not why an outcome has occurred. This analysis sought to determine how psychological factors assessed at baseline influenced response to personalised nutrition. Design/methodology/approach: Web-based, randomised, controlled trial (RCT) was conducted across seven European countries. Volunteers, both male and female, aged over 18 years were randomised to either a non-personalised (control) or a personalised (treatment) dietary advice condition. Linear mixed model analysis with fixed effects was used to compare associations between internal and external health locus of control (HLoC), nutrition self-efficacy (NS-E) and self-report habit index (S-RHI) at baseline (N = 1444), with healthy eating index (HEI) and Mediterranean diet index (MDI) scores between conditions post-intervention (N = 763). Findings: An increase in MDI scores was observed between baseline and six months in the treatment group which was associated with higher NS-E (p