The trial design and methods have been presented in detail elsewhere . Briefly, 259 eligible type 2 diabetes patients were recruited between March 2003 and April 2004 from ten urban primary care clinics, using the electronic database of the central region of the largest health maintenance organisation in Israel (Clalit Health Services). Inclusion criteria were: (1) type 2 diabetes diagnosed within the last 10 years; (2) 30–65 years of age; (3) BMI between 27 and 34 kg/m2; (4) HbA1c levels 7–10%; (5) plasma triacylglycerol level 1.8–4.5 mmol/l; (6) creatinine <123.2 μmol/l; and (7) ≥3 months on the same medication. Exclusion criteria were: (1) proliferative diabetic retinopathy; (2) current insulin treatment; (3) active oncological or psychiatric disease; and (4) uncontrolled hypothyroidism or hyperthyroidism.
We identified 2,486 type 2 diabetes patients, 1,063 (42.8%) of whom met the inclusion criteria, and 644 (60.6%) of those were willing to participate. Before study entry, patients were asked to repeat laboratory tests and to undergo fundoscopy: 244 patients did not complete the tests and an additional 141 were excluded due to new findings, thus 259 patients were recruited. The trial flow is presented in Fig. 1.
Patients were recruited to the trial by the study coordinator (R. Abel). Prior to randomisation, participants entered a 2 week maintenance period, during which they continued their usual diet and kept a food diary. An external person, who had no involvement in participant recruitment and had no knowledge of any participant characteristics, then allocated patients to the different trial arms and participating dietitians, using a systematic sequence. Although a systematic sequence rather than randomisation was used, concealment of allocation was protected, i.e. neither the recruiter nor the potential participant could foresee to which arm the potential participant would be allocated, as allocation was performed centrally and both the potential participant and recruiter were blinded to the allocation procedure and its outcome. The allocation of patients to different dietitians ensured the equal distribution of patients assigned to the three different diets between participating dietitians.
The three dietary interventions were similar in total energy intake but varied in fat and carbohydrate constituents as follows: (1) the 2003 recommended American Diabetes Association diet (ADA)  (50–55% carbohydrate of mixed glycaemic index, 30% fat and 15–20% protein); (2) a low glycaemic index (LGI) diet (50–55% LGI carbohydrate, 30% fat, 15–20% protein); (3) a modified Mediterranean diet (MMD) (35% LGI carbohydrate, 45% fats high in monounsaturated fat content, 20% protein). Energy (97 kJ/kg body weight), sodium (up to 3 g/day), potassium (>3 g/day), calcium (~1,300 mg/day) and magnesium (>800 mg/day) contents were similar in all three diets.
The process of providing dietary advice was identical in all three intervention groups. All three diet plans were based on food groups, and participants could design their own plan, using these groups. The ADA diet included light whole wheat bread, whole rice, bran flakes, rice cakes, fruit, vegetables, low sugar jam and honey. The LGI diet replaced wheat with oats, bread and rice with lentils, chickpeas and white beans. The MMD included fish, replaced butter with olive oil and olive-based margarine, and nuts and almonds. All diets included egg, chicken and turkey breast. All participants were also advised (using the same method of verbal advice in all three treatment arms) to undertake at least 30 min of aerobic activity three times a week, as this has been shown to have a beneficial effect on glucose tolerance and insulin sensitivity, as well as other cardiovascular risk factors . Participants met with their assigned dietitian every 2 weeks for 12 months for counselling. All dietitians worked according to a structured protocol for the 24 scheduled meetings and supervised patients from all three diets. Every other month, all patients were invited to a group meeting to discuss general health and emotional issues.
At baseline, participants completed a food frequency questionnaire [10, 11], a 24 h diet recall questionnaire and a physical activity questionnaire in the presence of a dietitian and underwent a medical examination by their treating physician which included taking blood samples after an overnight fast. These procedures were repeated after 6 months of follow-up and again after 12 months, except for the dietary questionnaires that were not administered again after 12 months. All blood tests were performed in a central laboratory of Clalit Health Services using standard procedures: ALT was determined according to the recommendations of the International Federation of Clinical Chemistry (IFCC) using a photometric method without pyridoxal phosphate (Hitachi 747; Indianapolis, IN, USA);fasting plasma glucose was measured by the photometric glucose oxidase technique (Hitachi 747); plasma insulin was measured by the immune-enzymatic technique (Immulite 2000; Siemens Healthcare Diagnostics, Deerfield, IL, USA) that does not cross-react with pro-insulin; total cholesterol and HDL-cholesterol (HDL-c) were measured using a photometric enzymatic method (Hitachi 747); and triacylglycerol using a photometric-glycerol phosphate-enzymatic method (Hitachi 747).
Pre-defined trial outcomes were: glycated haemoglobin, fasting plasma glucose, triacylglycerol (primary outcomes), and weight, BMI, waist and hip circumference, HDL-c and insulin resistance as assessed by the homeostasis model assessment (HOMA) . ALT was not measured as part of the trial protocol and was available only for those participants whose treating physicians included liver function tests as part of routine testing. It was estimated that 55 participants per arm would be required to detect a 20% change in triacylglycerol from baseline or a 10% difference between trial arms with 80% power and a 5% significance level.
All participants provided written informed consent. The study protocol was approved by the ethics committee of Soroka University Medical Center, Ben Gurion University, Beer Sheva, Israel.
ALT, fasting insulin, HOMA and triacylglycerol values had skewed distributions and were normalised using a natural-log transformation. The effects of the different diets on ALT levels at 6 and 12 months were examined both by comparing ALT levels between groups while controlling for baseline ALT using analysis of covariance, and by comparing ALT at 6 and 12 months to baseline ALT levels within groups (by a paired t test).
For the main analysis we included participants for whom both baseline and follow-up (at 6 or 12 months) measurements were available (n = 201, 78%). We also conducted a secondary analysis using a full intention to treat approach. This analysis included all randomised patients (n = 259). In this analysis the last available measurement was carried forward. In other words, for participants for whom ALT measurements at month 12 were missing, the ALT measurement obtained from month 6 was used and if that was unavailable, then the baseline measurement was included.
Finally, multivariable linear regression models were constructed to examine the effect of possible mediators (change between baseline and 6 months in BMI, waist to hip ratio, triacylglycerol and HOMA) on any association between diet and ALT levels at 6 months. All analyses were conducted in Stata version 9 (Stata Corporation, College Station, TX, USA).