A secondary analysis of PREDIMED-Plus shows that the curves for incident diabetes diverge within 6 months.
The combination of an energy-reduced Mediterranean diet and increased physical activity is better than a traditional unrestricted Mediterranean diet for preventing the development of type 2 diabetes in patients with metabolic syndrome and overweight or obesity, according to a secondary analysis of the PREDIMED-Plus trial.
Over 6 years of follow-up, there was a 31% lower relative risk of incident diabetes with the enhanced intervention, with the curves diverging within the first 6 months, the investigators report.
“Lifestyle intervention using an energy-reduced Mediterranean diet could be an important approach to reduce the incidence of diabetes,” Jordi Salas-Salvadó, MD, PhD (Universitat Rovira I Virgili, Reus, Spain), one of the senior authors of the study, told TCTMD. Adding exercise and cutting 600 kilocalories per day from one’s diet, particularly by eliminating foods that are not typically included in the Mediterranean diet, brings potential benefits, he added, “and this could be included as a routine clinical practice for diabetes prevention.”
“Lifestyle intervention using an energy-reduced Mediterranean diet could be an important approach to reduce the incidence of diabetes.” Jordi Salas-Salvadó
Though other types of diet could be used to stave off diabetes, Salas-Salvadó said the Mediterranean diet—with a focus on eating more fruits, vegetables, whole cereals, legumes, nuts, and extra-virgin olive oil and limiting meat, sugar-sweetened beverages, added sugars, and cream—is palatable and culturally acceptable in many countries.
This makes it “a highly sustainable, long-term weight loss option when combined with reduced energy intake,” he said.
The new analysis “confirms what we have known for a long time,” commented Alice Lichtenstein, DSc (Tufts University, Boston, MA). “Independent of the fat content of the diet, a high-quality diet consumed in amounts that result in weight loss, coupled with increased physical activity, results in beneficial health outcomes.”
It’s questionable whether extra-virgin olive oil is a critical component of the intervention or if “replacing sources of saturated fat (meat and cream) with sources of unsaturated fat more commonly consumed in the US (eg, soybean oil, canola oil) would have similar effects,” she added via email. “I suspect it would.”
Enhancing the Mediterranean Diet Impact
The original PREDIMED trial showed that an ad libitum Mediterranean diet supplemented with either extra-virgin olive oil or mixed nuts reduced diabetes incidence compared with a low-fat diet, even with only a small amount of weight loss.
Building on those findings, the PREDIMED-Plus trial, conducted at 23 centers in Spain, was designed to test whether caloric restriction and physical activity could provide additional benefits compared with a traditional Mediterranean diet in individuals ages 55 to 75 years with metabolic syndrome, overweight or obesity, and no cardiovascular disease at baseline. One-year interim data showed that the enhanced intervention reduced body weight, waist circumference, and other cardiometabolic risk factors.
The current prespecified secondary analysis, published online Monday in Annals of Internal Medicine, with lead authors Miguel Ruiz-Canela, PharmD, PhD, and Dolores Corella, PharmD, PhD (both from Instituto de Salud Carlos III, Madrid, Spain), focused on the long-term effects of the intervention on incident diabetes in participants who were free from diabetes at baseline.
The analysis included 4,746 participants (mean age 64.9 years; 50% women) who had been randomized to the enhanced intervention or to the Mediterranean diet as used in the original PREDIMED trial. The intervention included a planned energy reduction of 600 kilocalories per day in the context of a Mediterranean diet; recommendations for progressively increasing aerobic physical activity, strength, flexibility, and balance exercises; and behavioral support for weight loss. The control group received educational sessions on how to follow the diet, but no advice on physical activity or weight loss.
After 6 years, 12.0% of control participants and 9.5% of those receiving the intervention developed type 2 diabetes (adjusted HR 0.69; 95% CI 0.59-0.82). The absolute risk reduction was greater in men than in women (P = 0.035 for interaction), a finding that could be related to differences in weight loss, Salas-Salvadó said, adding, however, that further research is needed to explore this question.
Participants in the intervention group had better adherence to their diet, higher physical activity levels, larger reductions in body weight and waist circumference, and less use of antidiabetic drugs compared with those in the control group.
Challenges for US Adoption
In an accompanying editorial, Sharon Herring, MD, and Gina Tripicchio, PhD (both from Temple University, Philadelphia, PA), suggest that use of the energy-reduced Mediterranean diet tested in PREDIMED-Plus may not work in all areas of the world.
“Consumption of [this diet] may be particularly challenging in the United States where prevalence of CVD events, prediabetes, and type 2 diabetes remain critically high among adult populations, especially for those patients living in under-resourced neighborhoods where healthy food options are limited,” they write.
Moreover, prices for extra-virgin olive oil have shot up in recent years in the US “due to a combination of factors including climate change, rising production costs, supply chain disruptions, and now tariffs,” Herring and Tripicchio say. Issues with access to and reimbursement of prevention services may also make it difficult for American patients to achieve the high degree of contact with dieticians seen in the trial.
“As the investigators acknowledge,” they write, “more studies will be needed to replicate these results using a lower-intensity intervention to ensure adequate reach among the populations that need it most.”
Nonetheless, this analysis highlights the importance of diet quality and lifestyle modification to prevent chronic diseases even amidst the growing popularity of medications that can treat obesity and diabetes and reduce CVD events, the editorialists say. “Ultimately, this study contributes to the strong evidence base in support of the Mediterranean diet as an optimal dietary pattern for long-term health.”
The message, Salas-Salvadó said, “is that this multicomponent lifestyle modification could be a good strategy in order to reduce diabetes incidence.”
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