Jan. 07--Even without weight loss, adhering to a diet rich in fresh produce,
chicken, fish and olive oil is 40% more effective in heading off the development
of Type 2 diabetes than following a low-fat diet, a new study has found.
The research suggests that for the nation's 78 million obese adults, a diet that
minimizes red meat and sweets but incorporates plant-based fats may be a
sustainable way to improve health -- even if permanent weight reduction proves
The findings add to mounting research that suggests a traditional Mediterranean
diet may be easier to adhere to and more likely to improve health than more
Compared with those on a low-fat diet, trial participants whose
Mediterranean-style diet was supplemented with a daily dose of tree nuts --
almonds, walnuts and hazelnuts -- were 18% less likely to develop Type 2
diabetes. The researchers called that a positive trend but acknowledged that the
difference fell short of demonstrating beyond doubt the superiority of such a
diet over a standard low-fat diet.
Published Monday in the Annals of Internal Medicine, the latest entry in the
diet fray followed for more than four years a group of 3,541 older Spaniards who
were at high risk of developing cardiovascular disease. They were a subgroup of
a larger clinical trial that demonstrated the effectiveness of the Mediterranean
diet in reducing the risk of heart attacks and strokes.
That trial of 7,447 subjects -- documented in February in the New England
Journal of Medicine -- found that those placed on a Mediterranean diet
supplemented with either nuts or extra-virgin olive oil were 30% less likely
than those prescribed a low-fat diet to suffer a heart attack, stroke or death
due to cardiovascular disease.
Nearly half of those recruited for the parent trial already had Type 2 diabetes.
The subjects used in the current subgroup analysis started the trial with at
least three risk factors for developing premature cardiovascular disease: They
were active smokers; were overweight or obese; had a family history of premature
heart disease; or had hypertension or worrisome cholesterol readings. None had
been diagnosed with Type 2 diabetes at the start of the trial.
Some 273 participants went on to develop Type 2 diabetes. Among those in the
Mediterranean diet-supplemented-with-extra-virgin-olive-oil arm, 6.9% developed
diabetes; among those in the Mediterranean-diet-plus-nuts group, 7.4% did so;
and among the low-fat dieters, 8.8% developed Type 2 diabetes.
Dr. Meir J. Stampfer, professor of medicine and epidemiology at Harvard
University, called the research published Monday a significant step in further
demonstrating the clinical benefits of the diet that until recently predominated
in southern Europe. In showing the Mediterranean diet to be sustainable and
beneficial, Stampfer said, the study should help put to rest many
health-conscious Americans' aversion to nuts and oils, which are as
calorie-dense as they are rich in unsaturated fats.
But Dr. David Heber of UCLA's Center for Human Nutrition cautioned that
Americans should not give up efforts to cut fat from their diets in a bid to
improve health. He pointed to copious evidence supporting a widely available
regimen known as the Diabetes Prevention Program: When people at risk for
diabetes lose 5% to 10% of their body weight using a program that reduces
calorie and fat consumption and boosts their exercise, they drive down the
likelihood of developing diabetes over the next five years by close to 60%.
"Saying that it's beneficial to consume more olive oil, which has over 100
calories per tablespoon, without weight loss encourages magical thinking about
diabetes," Heber added. For obese patients, he said, driving down one's risk of
developing Type 2 diabetes requires weight management.
Dr. James B. Meigs, an internal medicine specialist at Harvard, noted that the
latest research suggests a Mediterranean diet drives down diabetes risk as much
as preventive use of the drug metformin. But that's still only half as powerful
an effect as that seen in subjects participating in the Diabetes Prevention
Program, which recommends at least 30 minutes a day of exercise and a low-fat,
Meigs said that while physicians still should advise obese patients to lose
weight and exercise more, he sees "little harm ... of also encouraging"
In the parent trial, subjects were urged to minimize sodas and fats that came in
spreadable form, as well as limit consumption of commercially baked sweets and
pastries to three times a week. They were told either to eat about a quarter-cup
a day of either almonds, walnuts or hazelnuts, or to consume at least 4
tablespoons a day of extra-virgin olive oil.
Mediterranean dieters were told they could drink wine moderately -- about seven
glasses per week.
Aside from those guidelines, subjects in the Mediterranean diet arms of the
trial had an "energy unrestricted" diet: They did not have a calorie limit, and
fats made up between 35% and 40% of their daily calorie intake.
Low-fat dieters were told to avoid nuts and vegetable oils of all kinds, to
limit store-bought sweets to less than one per week and to remove visible fat
from meats. In addition to fruits and vegetables, they were encouraged to eat
three servings of low-fat dairy products and three or fewer servings of bread,
potatoes, pasta or rice each day.
The researchers also reported that, compared with subjects in the low-fat arm of
their trial, those randomized into the two Mediterranean diet arms showed much
stronger adherence to the guidelines.
"These differences were probably critical" to the divergent patterns of diabetes
between those in the Mediterranean diet groups and those in the low-fat diet
group, they wrote.
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