Effect of a Transtheoretical Model-based intervention on fruit and vegetable intake according to perception of intake adequacy: A randomized controlled community trial

Abstract

Interventions based on the Transtheoretical Model (TTM) are usually effective at increasing fruit and vegetable (FV) intake, but it is not known whether individuals with misperceived intake [e.g., in pseudomaintenance (PM)] for FV intake also benefit from these interventions. This study aims to describe the effectiveness of a TTM-based intervention for FV intake according to baseline perception of intake adequacy. A randomized controlled community trial was carried out with 3414 users of a health promotion service in Belo Horizonte, Brazil, aged 20 years or over, in 2013–2014. FV intake was estimated using a validated instrument. PM was identified when participants had insufficient FV intake and thought their intake was adequate. The intervention group (IG) received a TTM-based intervention, and the control group (CG) received usual care. Baseline FV intakes were lower among individuals in PM compared to those with a concordant perception (CP). In both the IG and CG, FV intake increased among those in PM. Fruit intake remained stable, and vegetable intake decreased among those with CP. Generalized estimating equations revealed a significant effect of the intervention on fruit intake at follow-up, which was slightly higher among those in PM. We conclude that participants in PM were partially sensitive to the intervention and improved fruit intake at follow-up. We suggest that future studies emphasize vegetable intake and elucidate how TTM pillars (self-efficacy, decisional balance, processes of change) can be best used to increase FV intake.