Aims/hypothesisThe study aimed to compare the effects of a 2 year intervention with a low-fat diet (LFD) or a low-carbohydrate diet (LCD), based on four group meetings to achieve compliance.MethodsThis was a prospective randomised parallel trial involving 61 adults with type 2 diabetes consecutively recruited in primary care and randomised by drawing ballots. Patients that did not speak Swedish could not be recruited. The primary outcomes in this non-blinded study were weight and HbA1c. Patients on the LFD aimed for 55–60 energy per cent (E%) and those on LCD for 20 E% from carbohydrate.ResultsThe mean BMI and HbA1c of the participants were 32.7 ± 5.4 kg/m2 and 57.0 ± 9.2 mmol/mol, respectively. No patients were lost to follow-up. Weight loss did not differ between groups and was maximal at 6 months: LFD −3.99 ± 4.1 kg (n = 31); LCD −4.31 ± 3.6 kg (n = 30); p < 0.001 within groups. At 24 months, patients on the LFD had lost −2.97 ± 4.9 kg and those on LCD −2.34 ± 5.1 kg compared with baseline (p = 0.002 and p = 0.020 within groups, respectively). HbA1c fell in the LCD group only (LCD at 6 months −4.8 ± 8.3 mmol/mol, p = 0.004, at 12 months −2.2 ± 7.7 mmol/mol, p = 0.12; LFD at 6 months −0.9 ± 8.8 mmol/mol, p = 0.56). At 6 months, HDL-cholesterol had increased with the LCD (from 1.13 ± 0.33 mmol/l to 1.25 ± 0.47 mmol/l, p = 0.018) while LDL-cholesterol did not differ between groups. Insulin doses were reduced in the LCD group (0 months, LCD 42 ± 65 E, LFD 39 ± 51 E; 6 months, LCD 30 ± 47 E, LFD 38 ± 48 E; p = 0.046 for between-group change).Conclusions/interpretationWeight changes did not differ between the diet groups, while insulin doses were reduced significantly more with the LCD at 6 months, when compliance was good. Thus, aiming for 20% of energy intake from carbohydrates is safe with respect to cardiovascular risk compared with the traditional LFD and this approach could constitute a treatment alternative.Trial registration:ClinicalTrials.gov NCT01005498Funding:University Hospital of Linköping Research Funds, Linköping University, the County Council of Östergötland, and the Diabetes Research Centre of Linköping UniversityElectronic supplementary materialThe online version of this article (doi:10.1007/s00125-012-2567-4) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

BackgroundIn the clinic setting both fasting levels of glucose and the area under the curve (AUC) of glucose, by determination of HbA1c levels, are used for risk assessments, in type 2 diabetes (NIDDM). However little is known about postprandial levels, and hence AUC, regarding other traditional risk factors such as insulin and blood-lipids and how this is affected by different diets.ObjectiveTo study postprandial effects of three diets, during a single day, in NIDDM.MethodsA low-fat diet (45–56 energy-% from carbohydrates), and a low-carbohydrate diet (16–24 energy-% from carbohydrates) was compared with a Mediterranean-style diet (black coffee for breakfast and the same total-caloric intake as the other two diets for lunch with red wine, 32–35 energy−% from carbohydrates) in a randomized cross-over design. Total-caloric intake/test-day at the clinic from food was 1025–1080 kCal in men and 905–984 kCal in women. The test meals were consumed at a diabetes ward under supervision.ResultsTwenty-one participants were recruited and 19 completed the studies. The low-carbohydrate diet induced lower insulin and glucose excursions compared with the low-fat diet (p<0.0005 for both AUC). The insulin-response following the single Mediterranean-style lunch-meal was more pronounced than during the low-fat diet lunch (insulin increase-ratio of the low-fat diet: 4.35±2.2, of Mediterranean-style diet: 8.12±5.2, p = 0.001) while postprandial glucose levels were similar. The increase-ratio of insulin correlated with the elevation of the incretin glucose-dependent insulinotropic-polypeptide following the Mediterranean-style diet lunch (Spearman, r = 0.64, p = 0.003).ConclusionsThe large Mediterranean-style lunch-meal induced similar postprandial glucose-elevations as the low-fat meal despite almost double amount of calories due to a pronounced insulin-increase. This suggests that accumulation of caloric intake from breakfast and lunch to a single large Mediterranean style lunch-meal in NIDDM might be advantageous from a metabolic perspective.Trial RegistrationClinicalTrials.gov NCT01522157 NCT01522157

Weight-changes did not differ between the diet groups while improvements in HRQoL only occurred after one year during treatment with LCD. No changes of HRQoL occurred in the LFD group in spite of a similar reduction in body weight.