Older adults who stick with a traditional Mediterranean diet rich in plant-based fats may help lower their risk of type 2 diabetes, even without counting calories or shedding weight, new research hints.
In a study of 418 older Spanish adults, researchers found that those instructed to follow a Mediterranean diet were less likely to develop diabetes over four years than those instructed to follow a low-fat diet.
About 10% developed the disease, versus 18% in the low-fat group. And weight loss did not appear necessary to gain the benefit.
The findings, reported in the journal Diabetes Care, may sound too good to be true.
Curbs metabolic syndrome
But they back up previous work by the same researchers showing that the Mediterranean diet, even without weight loss, appeared to curb the risk of metabolic syndrome, a collection of risk factors for diabetes that includes abdominal obesity, high blood pressure and elevated blood sugar and triglycerides.
However, even if the eating pattern brings benefits in the absence of weight loss, that does not negate the importance of regular exercise or calorie-consciousness, a spokesperson for the American Dietetic Association said.
Instead, the findings support existing dietary advice for people with diabetes and those at risk of the disease, said Constance Brown-Riggs, a registered dietician and certified diabetes educator based in Massapequa, New York.
"This pretty much backs up what we've been recommending," Brown-Riggs said.
The traditional Mediterranean diet is generally high in vegetables, fibre-rich grains, legumes, fish and plant-based sources of unsaturated fat, particularly olive oil and nuts, while being low in red meat and high-fat dairy, prime sources of saturated fat.
All of those features are healthy choices for anyone, Brown-Riggs pointed out.
But the study, she added, "does not, by any means, say that you don't have to exercise." Nor does it mean that calories are unimportant, she said.
For the study, researchers led by Dr Jordi Salas-Salvado of the University of Rovira i Virgili in Reus, Spain, followed 418 initially diabetes-free adults between the ages of 55 and 80. Each had at least three risk factors for heart disease, such as high blood pressure, smoking or excess weight.
At the outset, the men and women were randomly assigned to follow one of three diets: a traditional Mediterranean diet with added emphasis on boosting consumption of olive oil, a rich source of monounsaturated fat; the same diet, with a focus on getting polyunsaturated fats from nuts; or a low-fat diet that encouraged cutting down on all types of fat.
In addition, participants in the olive-oil group were given a free allotment of the oil (a litre per week), and those in the nut group were given enough mixed nuts to have about an ounce per day.
None of the groups were told to limit calories or get more exercise.
Over the next four years, the researchers found, 10% to 11% of participants in the two Mediterranean groups developed diabetes. That compared with 18% of those in the low-fat diet group.
When the researchers accounted for a number of other factors such as participants' weight, smoking history and reported exercise levels, the Mediterranean diet itself was linked to 52% reduction in diabetes risk compared with the low-fat diet.
Moreover, both Mediterranean diet groups showed a lower diabetes risk over time without evidence that weight loss was the reason, according to Salas-Salvado's team.
When comparing participants who did or did not develop diabetes, the researchers found that average weight and exercise levels were the same in the two groups at the end of the study.
In contrast, participants in the low-fat group who remained diabetes-free did lose a few pounds, on average. But those who eventually developed diabetes gained a few pounds, on average.
The findings support the idea that components of the Mediterranean diet have health benefits independent of any effects on weight.
Past research in this same study group found that participants on the diet had improvements in blood sugar levels and sensitivity to blood-sugar-regulating hormone insulin, in the absence of weight loss.
In addition, the researchers note, the unsaturated fats in the Mediterranean diet are thought to have anti-inflammatory effects. Researchers believe that chronic, low-level inflammation in the body may have a role in a number of disease processes, including those underlying diabetes.
Brown-Riggs agreed that the diet's anti-inflammatory effects may help explain its health benefits. But she also pointed out that for overweight individuals, shedding excess pounds can curb inflammation as well. Exercise, meanwhile, can have numerous health benefits, including a reduced risk of heart disease.
So calorie control and regular exercise should remain goals, according to Brown-Riggs.
She also cautioned against seeing olive oil, or any single component of the Mediterranean diet, as a magic bullet.
"Sometimes individuals can get hung up on one item, like olive oil," she said, "But what we're talking about here is an overall eating pattern, and an overall lifestyle."
(Reuters Health, Amy Norton, October 2010)