The other half put on a low-fat diet based on American Heart Association guidelines. The diet was rich in whole grains and restricted fats, sweets and high-fat snacks. Women and men were likewise restricted to 1,500 and 1,800 calories per day, respectively. But unlike the Mediterranean diet group, they received no more than 30 percent of calories from fat and no more than 10 percent of calories from saturated fat.
The participants received dietary advice from nutritionists and dietitians during monthly sessions for the first year and every other month thereafter for the duration of the four-year study.
The patients kept diaries to record their food intake, which the researchers used, along with counseling session attendance records, to assess their adherence to the diet.
These self-reported diet details may have limited the accuracy study since researchers could not directly determine what the patients ate, the authors noted.
Another limitation was that both patients and providers knew to which diet the patients were assigned. Thus, doctors who prescribed diabetes medications to patients knew which diet the patients were on, which could have introduced bias.
"Perhaps most important," the authors wrote, was that "the findings reinforce the message that benefits of lifestyle interventions should not be overlooked despite the drug-intensive style of medicine fueled by the current medical literature."