January 6th, 2014

Mediterranean Diet Protects Against Diabetes, Regardless of Weight Loss

Even if it doesn’t lead to weight loss, a Mediterranean diet could help prevent the onset of type 2 diabetes, according to a subanalysis of last year’s influential PREDIMED study. In the main trial, reported in the New England Journal of Medicine, nearly 7500 people at high risk for cardiovascular disease were randomized to a low-fat diet or a Mediterranean diet supplemented by either extra-virgin olive oil (EVOO) or nuts. After nearly 5 years’ follow-up, the study was stopped early because of a significant reduction in cardiovascular events in the Mediterranean diet groups.

The new paper, published in the Annals of Internal Medicine, examines the development of diabetes — a prespecified secondary outcome — among the 3541 participants who did not have diabetes at baseline and for whom the follow-up diabetes status was available. After 4.1 years’ follow-up, there was a significant, 30% reduction in the risk for diabetes in the combined Mediterranean diet groups compared with the low-fat diet group (HR 0.70,  CI 0.54 – 0.92). Separately, the reduction was significant in the EVOO group but not in the nuts group. New-onset diabetes had occurred in 6.9% of people in the EVOO group, 7.4% in the nuts group, and 8.8% in the control group.

The differences in outcome appeared to be unrelated to weight loss, as the differences in weight loss across the groups were “negligible.” The authors explain that the major goal of the trial was “to change the overall dietary pattern,” and they did not attempt to reduce calories or increase physical activity.

It should be noted that more patients were lost to follow-up in the control group than in the Mediterranean diet groups (10.5% in the control group versus 6.9% in the nuts group and 4.1% in the EVOO group). The authors warn that any conclusions must be considered exploratory given that this was a substudy based on a subgroup of a larger trial.

Nevertheless, they conclude that PREDIMED “provides strong evidence that long-term adherence to a Mediterranean diet supplemented with EVOO without energy restrictions, which is high in monounsaturated fat and bioactive polyphenols, results in a substantial reduction in the risk for type 2 diabetes among older persons with high cardiovascular risk. Of note, this dietary pattern is palatable and has a high potential for long-term sustainability, with obvious public health implications for primary prevention of diabetes.”

3 Responses to “Mediterranean Diet Protects Against Diabetes, Regardless of Weight Loss”

  1. As a long-standing advocate of the Mediterranean Diet, I am grateful that PREDIMED reported more positive findings, and again rejoiced in that it was randomized. Wonder about what percentage of qualifying individuals in this category will switch, even though it is so palatable, especially with feta and walnuts. From time to time, adding some fruit, such as mandarin orange slices, livens it up differently.

    Recently the Mediterranean Diet has not escaped controversy, with the role of monounsaturated fat now being challenged. I will still enjoy liberal amounts of olive oil in my Greek salads, however, even if an RCT reports it is not needed for the protective effects… but I am confident it will be some time before that occurs.

    Unfortunately I must report that now few Greeks adhere to their own traditional fare that has received so much attention. Obesity is on the rise, especially high among children.

  2. I was dismayed by the announcement of the 10 diets US News chose to lead their “diet issue”. The issue was an extravaganza, where every diet had some good in it, and popularity, opinion, votes for ease in following the diets, simplicity, taste etc. were all given consideration in finalizing the priority of diets that “won.”
    Folks, an opportunity was lost for science, and another won by media fanfare. Now that 70% of readers, writers, typesetters, train conductors, food handlers, teachers, nurses and doctors–and everyone in this country is either overweight or obese, and the super-obese are growing fastest, isn’t it about time to say some effort is needed for weight loss, and if a diet is a snap to use, it is not a great diet for this purpose. The inclusion of the Slim-fast, despite the hundreds of testimonials available (of very little value in the evidence hierarchy) is most difficult to believe, when healthier shakes can be made at home from whole food.
    Which do we want, politically correct euphemistic feel-good talk for those who want to lose weight but cant, or the absolute, hard truth based upon science and nothing else. Yes a diet you can stick to is the best for you, but this too is really a matter of calorie intake, and there are many ways to achieve that. Further, the ability of some of the easy, popular diets are the ones with the greatest potential for manipulation and cheating.
    Finally, to include diets that are so peripheral to good science, when even good science can barely help because of the barriers, furthers the notion that fad diets deserve the very place at the table that time-honored, solid ones hold. The alkali diet used for analysis was cleaned up from most others offered on sites, but the striking amount of misinformation given on those sites should give pause about what people will do once seeing that it is even partly condoned by experts. All of those diets, even when completed, will unfortunately have little effect upon the national weight after a few months.
    After so many words and space devoted to dieting, I was overcome with even more fear about the future, when cardiovascular risk from crushingly high prevalences of morbid obesity, diabetes, MetSyn, and NALFD-NASH will be faced by an already stretched, strained, and unstable health system.

    Years ago, The ACSM and Uncle Sam believed the recommendations for physical activity to prevent disease was set too high, since Americans were not raising their exercise level. So they diluted the advice, making activity easier (ie dumbing it down), thinking it would at least bring more individuals to perform some activity, even if it was not fully protective. This happened a third time, with little effect. Looking back, the participation in physical activity was a straight line from the early 1980s to the present, as those guidelines changed. Not only is there a lesson in that result, but now it seems that even the self-reporting of physical exercise was grossly inflated. In the Jan 2014 issue of Med Sci Sports Exercise, what was formerly suspected–gross exaggeration of activity duration in surveys, was confirmed using accelerometers. So when a man reported 50 minutes of moderate to vigorous activity, it is likely he only performed only 20% to 46% of that amount. In other words, easing the bar for the minimum exercise was accompanied by a decrease in activity, since these reporting biases were not as prevalence in those early years.