Primary prevention of type 2 diabetes through nutritional counseling.

P revious studies have reported convincing evidence that type 2 diabetes can be prevented by the adoption of a healthy lifestyle in overweight subjects with impaired glucose tolerance (1,2). Although intensive lifestyle intervention can result in significant improvements in a range of clinical and metabolic variables, it is uncertain whether nutritional intervention programs are feasible in the health care system of developing countries (3). The purpose of this study was to evaluate the impact of low-cost nutritional intervention in changing the lifestyle of adults attending a primary health care center in São José do Rio Preto, São Paulo State, Brazil. We carried out a randomized controlled trial. Of the 259 volunteers (203 women and 56 men) contacted from April 2000 to March 2001, 104 eligible nondiabetic subjects (83 women and 21 men, aged 30–65 years, BMI 24–35 kg/m) were randomly assigned to two groups: nutritional counseling and control. Participants in the control group did not receive any individualized intervention during follow-up but received the same health check and blood sampling as the intervention group. Each subject in the intervention group received three individualized nutritional counseling sessions during the first 6 months aimed at increasing intake of fruits (at least two servings per day), vegetables (at least five servings per day), and skimmed dairy products (two or three servings per day), together with reduced intake of saturated fat ( 10% of the calories by reducing red meat [less than two servings per day]) and maintaining consumption of total fat at 30% of calories. After the second health check 6 months after baseline, the subjects did not receive any further intervention. The significance of differences between groups was tested by 2 analysis or Student s t test. At baseline, characteristics and dietary intake of energy and macronutrients were similar between groups. After 6 months of follow-up, the mean weight reduction in the intervention group ( 3.1%) was greater than in the control group (0.4%). Significantly greater improvements were seen at the 6-month follow-up in waist circumference ( 2% vs. 0.2%), total cholesterol ( 12.3% vs. 0.2%), LDL cholesterol ( 15.5% vs. 4%), and fasting plasma glucose ( 5.6% vs. 0.1%) in the intervention group compared with the control group (P 0.05). At the 12-month follow-up visit, when we evaluated the maintenance of lifestyle changes, the differences in weight ( 3.1% vs. 0.5%) and waist circumference ( 2% vs. 0.1%) remained greater in the intervention group (P 0.01). Both groups reduced serum total cholesterol after 1 year of follow-up. The present study provides evidence for the impact of nutritional intervention programs on well-known risk factors for type 2 diabetes and related diseases among overweight subjects at primary health care centers. A second finding was the significant weight loss and decreased waist circumference, total cholesterol, and LDL cholesterol with only three individualized dietary sessions at the 6-month follow-up, suggesting that less intensive lifestyle programs, with limited resources, are effective in changing food consumption and improving metabolic control and quality of life.