Factors associated with successful dietary changes in an energy-reduced Mediterranean diet intervention: a longitudinal analysis in the PREDIMED-Plus trial
Authors: Fernandez-Lazaro Cesar I. , Toledo Estefanía , Buil-Cosiales Pilar , Salas-Salvadó Jordi , Corella Dolores , Fitó Montserrat , Martínez J. Alfredo , Alonso-Gómez Ángel M. , Wärnberg Julia , Vioque Jesús , Romaguera Dora , López-Miranda José , Estruch Ramon , Tinahones Francisco J. , Lapetra José , Serra-Majem Luís , Bueno-Cavanillas Aurora , Tur Josep A. , Martín Sánchez Vicente , Pintó Xavier , Delgado-Rodríguez Miguel , Matía-Martín Pilar , Vidal Josep , Ros Emilio , Vázquez Clotilde , Daimiel Lidia , SanJulián Beatriz , García-Gavilán Jesús F. , Sorlí Jose V. , Castañer Olga , Zulet M. Ángeles , Tojal-Sierra Lucas , Pérez-Farinós Napoleón , Oncina-Canovas Alejandro , Moñino Manuel , Garcia-Rios Antonio , Sacanella Emilio , Bernal-Lopez Rosa M. , Santos-Lozano José Manuel , Vázquez-Ruiz Zenaida , Muralidharan Jananee , Ortega-Azorín Carolina , Goday Alberto , Razquin Cristina , Goicolea-Güemez Leire , Ruiz-Canela Miguel , Becerra-Tomás Nerea , Schröder Helmut , Martínez González Miguel A. ,   for the PREDIMED-Plus investigators
Published: November 2021

Abstract
Purpose
Long-term nutrition trials may fail to respond to their original hypotheses if participants do not comply with the intended dietary intervention. We aimed to identify baseline factors associated with successful dietary changes towards an energy-reduced Mediterranean diet (MedDiet) in the PREDIMED-Plus randomized trial.

Methods
Longitudinal analysis of 2985 participants (Spanish overweight/obese older adults with metabolic syndrome) randomized to the active intervention arm of the PREDIMED-Plus trial. Dietary changes were assessed with a 17-item energy-reduced MedDiet questionnaire after 6 and 12 months of follow-up. Successful compliance was defined as dietary changes from baseline of ≥ 5 points for participants with baseline scores < 13 points or any increase if baseline score was ≥ 13 points. We conducted crude and adjusted multivariable logistic regression models to identify baseline factors related to compliance.

Results
Consistent factors independently associated with successful dietary change at both 6 and 12 months were high baseline perceived self-efficacy in modifying diet (OR6-month: 1.51, 95% CI 1.25–1.83; OR12-month: 1.66, 95% CI 1.37–2.01), higher baseline fiber intake (OR6-month: 1.62, 95% CI 1.07–2.46; OR12-month: 1.62, 95% CI 1.07–2.45), having > 3 chronic conditions (OR6-month: 0.65, 95% CI 0.53–0.79; OR12-month: 0.76, 95% CI 0.62–0.93), and suffering depression (OR6-month: 0.80, 95% CI 0.64–0.99; OR12-month: 0.71, 95% CI 0.57–0.88).

Conclusion
Our results suggested that recruitment of individuals with high perceived self-efficacy to dietary change, and those who initially follow diets relatively richer in fiber may lead to greater changes in nutritional recommendations. Participants with multiple chronic conditions, specifically depression, should receive specific tailored interventions.

Trial registration
ISRCTN registry 89898870, 24th July 2014 retrospectively registered http://www.isrctn.com/ISRCTN89898870.