Intervention Ups Adherence to Low-Cal Mediterranean Diet

Roxanne Nelson RN, BSN

October 18, 2019

Individuals assigned to a reduced-calorie Mediterranean diet, physical activity, and behavioral support were more likely to adhere to the program than those who were just advised to follow an unrestricted Mediterranean diet, according to new findings.

Overall, there was significantly greater increase in adherence to the energy-reduced Mediterranean diet at 12 months. Improvements in diet quality, energy intake, and cardiovascular risk factors also were observed in the group consuming the reduced-calorie diet.

"The trial is ongoing," explained study author Miguel A. Martínez-González, MD, PhD, MPH, professor and chair of preventive medicine and public health at the University of Navarra, Spain. "These are only preliminary 1-year results, and we will be assessing cardiovascular events during a 6-year period."

The findings were published October 15 in JAMA.

The energy-reduced Mediterranean diet (er-MedDiet) features more restrictive limits for red and processed meats, butter, margarine, cream, and carbonated sweetened drinks than an unrestricted Mediterranean diet. It also recommends individuals not add sugar to beverages, limit white bread and refined cereals, and consume more whole grains. The authors hypothesized that an er-MedDiet may be the optimal model for overweight or obese individuals, and this served as the rationale for the current PREDIMED-Plus trial.

But a major challenge in evaluating nutritional interventions using a complete dietary pattern, as opposed to a single food or component, is participant adherence. However, initial results from a pilot study of 626 overweight/obese adults in this trial showed that good adherence is feasible. At 12 months, the intervention group also had decreased adiposity and improved cardiovascular risk factors.

In the current trial, Martinez-Gonzalez and colleagues examined adherence and changes in risk factors after 12 months, but in a cohort about 10 times larger than the pilot.

Reduced Risk

A total of 6874 adults, 55 to 75 years of age, with metabolic syndrome but without CVD were randomly assigned to an intervention that followed an er-MedDiet, promoted physical activity, and provided behavioral support (n = 3406) or to an energy-unrestricted Mediterranean diet (n = 3468).

All participants received allotments of extra-virgin olive oil (1 L/month) and nuts (125 g/month). The primary outcome was 12-month change in adherence, measured with the er-MedDiet score (range, 0 - 17; higher scores indicate greater adherence; minimal clinically important difference, 1 point).

The mean er-MedDiet score in the intervention group increased from 8.5 at baseline to 13.2 at 12 months and from 8.6 to 11.1, respectively, in the control group (between-group difference, 2.2; 95% CI, 2.1 - 2.4; P < .001).

The improvements observed in the er-MedDiet score in the intervention group represented a significant 55% relative increase over 12 months (95% CI, 55% - 56%; P < .001).

The authors also noted that there were significant reductions in the consumption of specific foods or food groups at the time of the interim analysis. Baseline consumption of refined grains, for example, was 779 g/week for both groups, but after 12 months had dropped by 535 g/week in the intervention group and 226 g/week in the control group, for a significant between-group difference of 309 g/week (95% CI, 340 - 277; P <.001).

Significant reductions in red meat consumption were also observed, with a between-group difference of 39 g/week (95%CI, 51 - 28; < .001) at 12 months.

Some of the greatest increases in intake were observed for vegetables, with a mean baseline consumption of 2168 g/week for participants in the intervention group and 2130 g/wk in the control group, and within-group differences after 12 months of 347 g/wk and 137 g/wk, respectively. The between-group difference of 210 g/wk was significant (95% CI, 157-263; P <.001).

Finally, when looking at CVD risk factors at 12 months, there were "significant and clinically meaningful" favorable changes for the intervention vs the control group as far as body weight, waist circumference, body mass index, high-density-lipoprotein cholesterol (HDL-C), non-HDL-C, total cholesterol:HDL-C ratio, triglycerides, and systolic and diastolic blood pressure.

"In my opinion, there is a need to include further nutritional support in health centers, including hiring dietitians," Martínez-González told | Medscape Cardiology. "This is costly, but the CV events are even more expensive."

Results Meaningful

In an accompanying editor's note, Philip Greenland, MD, Northwestern University Feinberg School of Medicine, Chicago, and senior editor of JAMA, notes that these interim results are "meaningful in several ways."

First, the greater adherence to diet among patients in the intervention group provides reassurance that this approach is having a measurable effect on diet and body weight. "This is an important intermediate step but not yet sufficient to inform new dietary recommendations," says Greenland.

"Second, the authors have demonstrated in this study and previous research that large-scale dietary intervention studies are practical if carefully conducted. The long-term main endpoint results are eagerly awaited."

The study was supported by the European Research Council, CIBER Fisiopatología de la Obesidad y Nutrición and Instituto de Salud Carlos III through the Fondo de Investigación para la Salud, which is cofunded by the European Regional Development Fund, the Recercaixa, the SEMERGEN grant, the International Nut and Dried Fruit Council-FESNAD, an AstraZeneca Young Investigators Award, grants from the Consejería de Salud de la Junta de Andalucía, a grant from the Generalitat Valenciana, and a grant of support to research groups 35/2011 (Balearic Islands Gov; FEDER funds).

Martínez-González reported having no disclosures; several coauthors disclose relationships with industry, as noted in the paper. Greenland has no disclosures.

JAMA. 2019;322:1486-1499 and 1500. Abstract, Editor's note

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