None of the interventions were significantly better than the others in lowering glucose parameters .
The Mediterranean diet reduced HbA1c significantly compared to usual care but not compared to the Palaeolithic diet .
The effect of alterations in dietary practice irrespective of weight loss on glycaemic control can not be concluded from the present review .
BACKGROUND Overweight or obese individuals with type 2 diabetes are encouraged to lose weight for optimal glucose management , yet many find this difficult .
Determining whether alterations in dietary patterns irrespective of weight loss can aid glucose control has not been fully investigated .
METHODS We conducted a systematic review and meta- analysis aim ing to determine the effects of a Mediterranean diet compared to other dietary interventions on glycaemic control irrespective of weight loss .
Effects of a Mediterranean-Style Diet on the Need for Antihyperglycemic Drug Therapy in Patients With Newly Diagnosed Type 2 Diabetes
Context Mediterranean-style diets improve control of coronary risk factors and hyperglycemia , but few direct comparisons of the diet with other st and ard diets have been done . Contribution In this r and omized clinical trial , patients with newly diagnosed type 2 diabetes who were assigned to a low-carbohydrate , Mediterranean-style diet had better glycemic control and were less likely to need oral antihyperglycemic therapy than patients assigned to a low-fat diet . Caution The trial was unblinded , and dietary intake was self-reported . Implication A low-carbohydrate , Mediterranean-style diet seems to be preferable to a low-fat diet for glycemic control in patients with newly diagnosed type 2 diabetes . The Editors The p and emic of type 2 diabetes is an enormous public health problem , with 380 million cases worldwide projected by 2025 ( 1 , 2 ) . Lifestyle intervention studies ( 3 ) have demonstrated large reductions in risk for type 2 diabetes that remain after lifestyle counseling is stopped ( 4 , 5 ) . Despite this beneficial effect , the American Diabetes Association ( ADA ) recommends that patients with newly diagnosed type 2 diabetes be treated with pharmacotherapy as well as lifestyle changes ( 6 ) . The rationale for combination therapy is presumably that each form of treatment alone is imperfect . Lifestyle changes are often inadequate because patients do not lose weight or regain weight or their diabetes worsens independent of weight ( 6 ) . Pharmacotherapy also often fails with time ( 7 ) , and some drugs have associated cardiovascular and other risks ( 8 , 9 ) . For those reasons , lifestyle changes proven to be more effective than what is typically recommended would be welcome . For example , Mediterranean-style ( MED ) diets with a high proportion of monounsaturated fat provide cardiovascular benefits and increase insulin sensitivity ( 1012 ) , and the ADA recommends low-carbohydrate or low-fat , calorie-restricted diets for weight loss in overweight and obese patients with type 2 diabetes ( 13 ) . However , few direct , long-term comparisons of the 2 diets in patients with diabetes have been done ( 11 ) . We conducted a r and omized trial to compare the effectiveness , durability , and safety of a low-carbohydrate MED diet and a low-fat diet on glycemic control in patients with newly diagnosed type 2 diabetes . Methods We conducted the trial between January 2004 ( first patient enrolled ) and September 2008 ( end of follow-up of the last patient ) at the research center of the Diabetes Clinic of the Azienda Ospedaliera Universitaria , Second University of Naples , Naples , Italy , in accordance with the Declaration of Helsinki and with the institutional review board 's approval . Screening Phase We recruited men and women with newly diagnosed type 2 diabetes by ADA criteria who had never been treated with antihyperglycemic drugs from the clinical practice s of trial investigators and screened them for eligibility . Inclusion criteria were age 30 to 75 years , body mass index ( BMI ) greater than 25 kg/m2 , and hemoglobin A1c ( HbA1c ) level less than 11 % . Participants also had to be sedentary ( < 1 hour of physical activity per week ) with no evidence of participation in weight-reduction programs and with a stable weight ( 2 kg ) in the past 6 months . Exclusion criteria included pregnancy or breastfeeding , use of any investigational drug in the previous 3 months , use of agents affecting glycemic control ( such as systemic glucocorticoids and weight loss drugs ) , and any condition that might compromise adherence to diet regimens . To minimize the likelihood of including participants with late-onset type 1 diabetes , we screened c and i date s by testing for antibodies to glutamate decarboxylase and measuring fasting plasma C-peptides . We excluded patients with positive antibodies or C-peptide levels less than 0.25 pmol/L ( < 0.76 ng/L ) . We also excluded patients with abnormal laboratory test results , including liver enzyme levels ( alanine aminotransferase , aspartate aminotransferase , and alkaline phosphatase ) greater than 3 times the upper limit of normal and serum creatinine levels greater than 123.8 mol/L ( > 1.4 mg/dL ) . We required that participants successfully self-monitor their diet and physical activity over a 2-week run-in period . We provided dietary education during that time that emphasized the importance of eating a healthy diet and being physically active for both weight loss and improvement of glycemic control . Participants were also taught to prepare their own meals at home . We encouraged all individuals who smoked to quit and provided self-help material s , referral to local programs , or both , as appropriate . R and omization and Blinding After obtaining informed consent , we r and omly assigned patients to 1 of the 2 study diets by using a computer-generated r and om-number sequence ( simple r and omization ) . Allocation was concealed in sealed study folders that were held in a central , secured location until after informed consent was obtained . The nurses who scheduled the study visits did not have access to the r and omization list , and laboratory staff did not know the participants ' group assignments . Staff members involved in the intervention were aware of group assignments , but those who assessed achievement of the primary outcome were blinded to the intervention . Participants received no financial compensation or gifts . Dietary Interventions We r and omly assigned patients to a low-carbohydrate MED diet or to a low-fat diet . The MED diet was rich in vegetables and whole grains and low in red meat , which was replaced with poultry and fish . We restricted energy intake to 1500 kcal/d for women and 1800 kcal/d for men , with the goal of no more than 50 % of calories from complex carbohydrates , based on evidence that , in the context of a MED diet , a carbohydrate content less than 50 % of daily energy is more beneficial than higher content for weight loss and cardiovascular risk reduction ( 14 ) . The diet had no less than 30 % calories from fat . The main source of added fat was 30 to 50 g of olive oil . The low-fat diet was based on American Heart Association guidelines ( 15 ) ; it was rich in whole grains and restricted additional fats , sweets , and high-fat snacks . We restricted energy intake to 1500 kcal/d for women and 1800 kcal/d for men , with the goal of no more than 30 % of calories from fat and no more than 10 % of calories from saturated fat . Nutritionists and dietitians gave dietary advice to participants in both groups in monthly sessions in the first year and bimonthly sessions thereafter . Participants kept diet diaries after being instructed how to record their intake using food models as examples of portion size and using actual weights or amounts in terms of common measures ( such as cups , teaspoons , and dessert spoons ) . We assessed adherence to the diets by session attendance and review of the diaries . Nondietary Interventions Patients in both groups also received guidance on increasing their level of physical activity , mainly walking for a minimum of 30 minutes per day , but also swimming or aerobic ball games . The physical activity program relied heavily on home-based exercise with gradual progression toward a goal of 175 minutes of moderate-intensity physical activity per week . Although walking was encouraged , participants were allowed to choose other types of moderate-intensity physical activity , and programs were tailored on the basis of the results of a baseline physical fitness test and safety concerns . We asked all patients to record occupational , household , and leisure time physical activity . Outcomes We followed patients for 4 years to assess trial outcomes . The primary outcome measure was time to introduction of antihyperglycemic drug therapy . Trial investigators were responsible for initiating drug therapy by the following protocol . As suggested by the ADA for clinical evaluation and management of diabetic patients ( 16 ) , we measured HbA1c at baseline and every 3 months thereafter . Participants who had a HbA1c level greater than 7 % were given an additional 3 months to reinforce dietary guidance and physical activity ; if the HbA1c level remained greater than 7 % , a drug regimen was introduced . Participants with an HbA1c level greater than 7 % at baseline were counted as having experienced the primary outcome if they still had that level at first follow-up . Trial investigators were also responsible for initiating or titrating antihypertensive or lipid-lowering therapy . Secondary outcome measures were changes in weight ( including BMI and waist circumference ) , glycemic control ( HbA1c , glucose , serum insulin , and adiponectin levels and homeostasis model assessment of insulin sensitivity ) , coronary risk factors ( lipid levels and blood pressure ) , and medications and meeting ADA coronary risk factor goals ( HbA1c level < 7 % , blood pressure < 130/80 mm Hg , and low-density lipoprotein cholesterol level < 2.59 mmol/L [ < 100 mg/dL ] ) ( 16 ) . Participants were weighed without shoes and in lightweight clothing to the nearest 0.1 kg at baseline and every month . Height at baseline ( for calculation of BMI ) was measured to the nearest millimeter with the use of a wall-mounted stadiometer ( Seca , Hamburg , Germany ) . Waist circumference was measured halfway between the last rib and the iliac crest . We measured HbA1c levels with high-pressure liquid chromatography by using the fully automated Glycosylated Hemoglobin Analyzer System ( Bio-Rad , Hercules , California ) traceable to the Diabetes Control and Complications Trial reference method , with a reference range of 4.0 % to 6.0 % . Insulin sensitivity in the fasting state was assessed with homeostasis model assessment and calculated with the following formula , as described by Matthews and colleagues ( 17 ) : fasting plasma glucose (mmol/L)fasting serum insulin (U/mL)/25 . High scores indicate low insulin sensitivity ( insulin resistance ) . We assayed plasma insulin and adiponectin levels by radioimmunoassay , as described elsewhere ( 18 ) . We performed assays for serum
None of the interventions were significantly better than the others in lowering glucose parameters .
The Mediterranean diet reduced HbA1c significantly compared to usual care but not compared to the Palaeolithic diet .
The effect of alterations in dietary practice irrespective of weight loss on glycaemic control can not be concluded from the present review .
BACKGROUND Overweight or obese individuals with type 2 diabetes are encouraged to lose weight for optimal glucose management , yet many find this difficult .
Determining whether alterations in dietary patterns irrespective of weight loss can aid glucose control has not been fully investigated .
METHODS We conducted a systematic review and meta- analysis aim ing to determine the effects of a Mediterranean diet compared to other dietary interventions on glycaemic control irrespective of weight loss .