Effect of a Nutritional and Behavioral Intervention on Energy-Reduced Mediterranean Diet Adherence Among Patients With Metabolic Syndrome: Interim Analysis of the PREDIMED-Plus Randomized Clinical Trial

Abstract

Importance: High-quality dietary patterns may help prevent chronic disease, but limited data exist from randomized trials about the effects of nutritional and behavioral interventions on dietary changes.

Objective: To assess the effect of a nutritional and physical activity education program on dietary quality.

Design, setting, and participants: Preliminary exploratory interim analysis of an ongoing randomized trial. In 23 research centers in Spain, 6874 men and women aged 55 to 75 years with metabolic syndrome and no cardiovascular disease were enrolled in the trial between September 2013 and December 2016, with final data collection in March 2019.

Interventions: Participants were randomized to an intervention group that encouraged an energy-reduced Mediterranean diet, promoted physical activity, and provided behavioral support (n = 3406) or to a control group that encouraged an energy-unrestricted Mediterranean diet (n = 3468). All participants received allotments of extra-virgin olive oil (1 L/mo) and nuts (125 g/mo) for free.

Main outcomes and measures: The primary outcome was 12-month change in adherence based on the energy-reduced Mediterranean diet (er-MedDiet) score (range, 0-17; higher scores indicate greater adherence; minimal clinically important difference, 1 point).

Results: Among 6874 randomized participants (mean [SD] age, 65.0 [4.9] years; 3406 [52%] men), 6583 (96%) completed the 12-month follow-up and were included in the main analysis. The mean (SD) er-MedDiet score was 8.5 (2.6) at baseline and 13.2 (2.7) at 12 months in the intervention group (increase, 4.7 [95% CI, 4.6-4.8]) and 8.6 (2.7) at baseline and 11.1 (2.8) at 12 months in the control group (increase, 2.5 [95% CI, 2.3-2.6]) (between-group difference, 2.2 [95% CI, 2.1-2.4]; P < .001).

Conclusions and relevance: In this preliminary analysis of an ongoing trial, an intervention that encouraged an energy-reduced Mediterranean diet and physical activity, compared with advice to follow an energy-unrestricted Mediterranean diet, resulted in a significantly greater increase in diet adherence after 12 months. Further evaluation of long-term cardiovascular effects is needed.

Trial registration: isrctn.com Identifier: ISRCTN89898870.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Ros reported receiving grants, personal fees, and nonfinancial support from the California Walnut Commission during the conduct of the study and grants, personal fees, nonfinancial support from Alexion; grants from Amgen and Pfizer; grants and personal fees from Sanofi Aventis; personal fees and nonfinancial support from Ferrer International, Danone, and Merck Sharp & Dohme; and personal fees from Amarin outside the submitted work. Dr Corella reported receiving grants from Instituto de Salud Carlos III during the conduct of the study. Dr Romaguera reported receiving grants from Instituto de Salud Carlos III, Spanish government during the conduct of the study and grants from Fundación AstraZeneca outside the submitted work. Dr Estruch reported receiving grants from Instituto de Salud Carlos III and olive oil for the trial from Fundacion Patrimonio Comunal Olivarero \during the conduct of the study and personal fees from Brewers of Europe, Fundación Cerveza y Salud, Interprofesional del Aceite de Oliva, Instituto Cervantes, Instituto Cervantes, Pernaud Richar, Fundación Dieta Mediterránea, Wine and Culinary International Forum; nonfinancial support from Sociedad Española de Nutrición and Fundación Bosch y Gimpera; and grants from Uriach Laboratories outside the submitted work. Dr López-Miranda reported receiving grants from Fondo de Investigaciones Sanitarias, Instituto de Salud Carlos III during the conduct of the study. Dr Matía-Martín reported receiving grants from Instituto de Salud Carlos III during the conduct of the study and personal fees from Organización Interprofesional Láctea outside the submitted work. Dr Vidal reported receiving grants from Instituto de Salud Carlos III during the conduct of the study. Dr Fiol reported receiving grants from Instituto de Salud Carlos III, Spanish government during the conduct of the study. Dr Arós reported receiving grants from Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias (Spain) and from CIBEROBN, Instituto de Salud Carlos III (Spain) during the conduct of the study. Dr Moñino reported receiving grants from Instituto de Salud Carlos III, Spanish government during the conduct of the study. Dr Bouzas reported received a Fernando Tarongí Bauzà grant. Dr Salas-Salvado reported receiving research support from the Instituto de Salud Carlos III, Ministerio de Educación y Ciencia, Departament de Salut Pública de la Generalitat de Catalunya, the European Commission, the California Walnut Commission, Patrimonio Comunal Olivarero, La Morella Nuts, and Borges S.A; receiving consulting fees or travel expenses from Danone, California Walnut Commission, Eroski Foundation, Instituto Danone, Nestle, and Abbott Laboratories, receiving nonfinancial support from Hojiblanca, Patrimonio Comunal Olivarero, and Almond Board of California; serving on the board of and receiving grant support through his institution from the International Nut and Dried Foundation and the Eroski Foundation; and grants and personal fees from Instituto Danone. No other disclosures were reported.

Figures

Figure 1.. Flow of Participants in a Study of the Effect of an Energy-Reduced Mediterranean Diet Among Adults With Metabolic Syndrome

Figure 2.. Changes in the Primary End Point of Diet Adherence in a Study of the Effect of an Energy-Reduced Mediterranean Diet (er-MedDiet) Among Adults With Metabolic Syndrome

Horizontal box plots are shown in which the middle line represents the median er-MedDiet score (range, 0-17; higher score indicates higher adherence), boxes represent the interquartile range (IQR), whiskers extend to the most extreme observed values with 1.5 × IQR of the nearer quartile, and the dots represent observed values outside that range.

Figure 3.. Changes in Risk Factors in a Study of the Effect of an Intervention Promoting an Energy-Reduced Mediterranean Diet Among Adults With Metabolic Syndrome

Participants in the intervention group were encouraged to follow an energy-reduced Mediterranean diet, accompanied by physical activity promotion and behavioral support, while participants in the control group were encouraged to follow the traditional Mediterranean diet with ad libitum caloric intake. Horizontal box plots are shown in which the middle line represents the within-group median change in observed risk factors, boxes represent the interquartile range (IQR), and whiskers extend to the most extreme observed values with 1.5 × IQR of the nearer quartile. All differences are expressed in common units of baseline SD of each factor for comparability. HDL indicates high-density lipoprotein; LDL, low-density lipoprotein.

Figure 4.. Risk Factors at 12 Months of Follow-up in a Study of the Effect of an Energy-Reduced Mediterranean Diet Among Adults With Metabolic Syndrome

Horizontal box plots are shown in which the middle line represents the median change in observed risk factors, boxes represent the interquartile range (IQR), whiskers extend to the most extreme observed values with 1.5 × IQR of the nearer quartile, and the dots represent observed values outside that range. HDL indicates high-density lipoprotein; LDL, low-density lipoprotein.