In type 2 diabetes, randomisation to advice to follow a low-carbohydrate diet transiently improves glycaemic control compared with advice to follow a low-fat diet producing a similar weight loss

Abstract

Aims/hypothesis: The 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.

Methods: This 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 HbA(1c). Patients on the LFD aimed for 55-60 energy per cent (E%) and those on LCD for 20 E% from carbohydrate.

Results: The mean BMI and HbA(1c) of the participants were 32.7 ± 5.4 kg/m(2) 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). HbA(1c) 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/interpretation: Weight 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 NCT01005498

Funding: University Hospital of Linköping Research Funds, Linköping University, the County Council of Östergötland, and the Diabetes Research Centre of Linköping University.

Figures

Fig. 1

Flow diagram of the study

Fig. 2

Comparison of weight reduction with an LCD, aiming to achieve 20 E% from carbohydrate (squares), and an LFD (circles), aiming for 55–60 E% from carbohydrates, during 2 years in patients with type 2 diabetes. The weight reduction did not differ between the groups (p = 0.33 for all time points)

Fig. 3

Comparison of the reduction in HbA1c levels following an LCD with the aim of achieving 20 E% from carbohydrate (squares), and an LFD (circles), aiming for 55–60 E% from carbohydrate, over 2 years in patients with type 2 diabetes. The reduction in HbA1c level was statistically significant within the low-carbohydrate group (p = 0.005 for all time points), but did not differ between the groups when compared at all time points (p = 0.76). To convert values for HbA1c in mmol/mol into %, divide by 10.929 and add 2.15