Table 1.
Characteristics of included studies.
| Study (Country) | Trial Design | Intervention Duration | Diet | N | Age, Mean ± SD (Years) |
Female, N (%) | FG, Mean ± SD (mg/dL) |
BMI, Mean ± SD (kg/m2) | Baseline T2DM | Inclusion Criteria |
|---|---|---|---|---|---|---|---|---|---|---|
| Goday 2016 [21] (Spain) |
Prospective, open-label, multi-centric, parallel group randomized controlled trial | 4 months | I: very low-calorie-ketogenic diet | 45 | 54.89 ± 8.81 | 30 (66.6) | 136.87 ± 34.43 | 33.25 ± 1.52 | Yes | Age: 30–65 years; BMI: 30–35 kg/m2 |
| C: low-calorie diet | 44 | 54.17 ± 7.97 | 28 (63.6) | 142.81 ± 44.26 | 32.88 ± 1.60 | |||||
| Jabekk 2010 [22] (Norway) |
Randomized controlled trial | 10 weeks | I: low carbohydrate, ketogenic diet | 8 | - | 8 (100) | 88.2 ± 5.4 | 32.9 ± 4.5 | No | Age: 20–40 years; BMI: ≥25 kg/m2 |
| C: regular diet | 8 | - | 8 (100) | 90.0 ± 5.4 | 31.7 ± 4.2 | |||||
| Myette-Cote 2018 [23] (Canada) |
Randomized controlled crossover trial | 4 days | I: low-carbohydrate high-fat diet | 11 | 64 ± 8 | 7 (63.6) | 151.2 ± 34.2 | 34.0 ± 8.0 | Yes | HbA1c >6.5% or FG >7.0 mmol/L or 2-h OGTT >11.1 mmol/L |
| C: low-fat low-glycemic index guidelines diet | 149.4 ± 37.8 | |||||||||
| Partsalaki 2012 [24] (Greece) |
Randomized controlled trial | 6 months | I: ketogenic diet | 21 | 12.8 ± 2.1 | 11 (52.4) | 84.3 ± 9.8 | 30.0 ± 4.3 | No | Age: 8–18 years; BMI: >95th percentile for gender and age |
| C: hypocaloric diet | 17 | 12.7 ± 2.8 | 10 (58.8) | 80.2 ± 17.6 | 28.1 ± 3.1 | |||||
| Sanz-Paris 1998 [25] (Spain) |
Randomized controlled trial | 120 min | I: low-carbohydrate, high-fat formulation | 27 | 65 ± 7 | 33 (64) | 185 ± 56 | 29.2 ± 2.7 | Yes | Age: 45–72 years; good glycemic control (mean HbA1c: 6.5 ± 0.9%) |
| C: high-carbohydrate, low-fat formulation | 25 | 170 ± 48 | ||||||||
| Saslow 2014 [26] (US) |
Single site, parallel group, balanced randomization (1:1) trial | 3 months | I: low-carbohydrate ketogenic diet | 16 | 64.8 ± 7.7 | 9 (56.3) | 124.4 ± 28.3 | 36.2 ± 8.2 | Yes(including prediabetes) | Age: ≥18 years;BMI: ≥25 kg/m2; HbA1c: ≥6.5% (T2DM) or >6% (prediabetes) |
| C: moderate-carbohydrate, calorie-restricted, low-fat diet | 18 | 55.1 ± 13.5 | 16 (88.9) | 140.6 ± 34.3 | 37.4 ± 6.4 | |||||
| Saslow 2017-1 [27] (US) |
Single site, parallel group, balanced randomization (1:1) trial | 12 months | I: low-carbohydrate ketogenic diet | 16 | 64.8 ± 7.7 | 9 (56.3) | - | 36.2 ± 8.2 | Yes(including prediabetes) | Age: ≥18 years; BMI: ≥25 kg/m2; HbA1c: ≥6.5% (T2DM) or >6% (prediabetes) |
| C: moderate-carbohydrate, calorie-restricted, low-fat diet | 18 | 55.1 ± 13.5 | 16 (88.9) | - | 37.4 ± 6.4 | |||||
| Saslow 2017-2 [28] (US) |
Parallel-group, balanced randomization (1:1) trial | 32 weeks | I: very low-carbohydrate ketogenic diet | 12 | 53.0 ± 10.2 | 6 (50) | - | - | Yes | Age: ≥18 years; BMI: ≥25 kg/m2; HbA1c: ≥6.5–9% |
| C: American Diabetes Associations’ “Create Your Plate” diet | 13 | 58.2 ± 6.7 | 9 (69) | - | - | |||||
| Sun 2019 [29] (China) |
Randomized controlled trial | 4 weeks | I: low-carbohydrate, ketogenic diet | 18 | 20.9 ± 3.7 | 18 (100) | 84.6 ± 7.2 | 25.0 ± 2.9 | No | Age: 18–30 years; BMI: ≥23 kg/m2; past 6-month weight variation: <2kg; sedentary lifestyle |
| C: normal diet | 17 | 21.6 ± 3.9 | 17 (100) | 82.8 ± 9.0 | 24.8 ± 3.2 | |||||
| Tay 2017 [30] (Australia) |
Single-center, parallel-groups, randomized controlled trial | 2 years | I: low-carbohydrate, high-unsaturated/low-saturated fat diet | 58 | 58 ± 7.6 | 21 (36) | 140.4 ± 37.8 | 34.2 ± 4.2 | Yes | Age: 35–68 years; BMI: 26–45 kg/m2; HbA1c: 7.0% or antidiabetic treatment |
| C: high-carbohydrate, low-fat diet | 57 | 58 ± 7.5 | 28 (49) | 151.2 ± 41.4 | 35.1 ± 4.1 | |||||
| Vazquez 1994 [31] (US) |
Randomized controlled trial | 28 days | I: ketogenic diet | 8 | 48 ± 3 | 8 (100) | 86.4 ± 5.4 | 41 ± 5 | No | BMI: 35 kg/m2 |
| C: nonketogenic very-low-calorie diet | 8 | 44 ± 5 | 8 (100) | 88.2 ± 7.2 | 37 ± 6 | |||||
| Westman 2008 [32] (US) |
Randomized controlled trial | 24 weeks | I: low-carbohydrate, ketogenic diet | 38 | 51.8 ± 7.3 | 29 (76.3) | 178.1 ± 72.9 | 37.7 ± 6.1 | Yes | Age: 18–65 years; BMI: 27–50 kg/m2; HbA1c: >6.0% |
| C: low-glycemic, reduced-calorie diet | 46 | 51.8 ± 7.8 | 37 (80.4) | 166.8 ± 63.7 | 38.5 ± 5.6 | |||||
| Yancy 2007 [33] (US) |
Randomized controlled trial (prospective analysis of volunteers from two clinical trials) | 24 weeks | I: low carbohydrate ketogenic diet | 27 | 43.8 ± 10.2 | 19 (70) | 87.1 ± 2.2 | 36.0 ± 4.9 | No | Age 18–65 years; BMI: 30–60 kg/m2 |
| C: low fat diet | 12 | 42.8 ± 7.3 | 9 (75) | 95.8 ± 3.1 | 36.0 ± 5.7 | |||||
| Yancy 2010 [34] (US) |
Randomized controlled trial | 48 weeks | I: low-carbohydrate, ketogenic diet | 72 | 52.9 ± 10.2 | 20 (28) | - | 39.9 ± 6.9 | No | Age: 18–70 years; BMI: 27–30 kg/m2 (plus obesity-related disease) or BMI: ≥30 kg/m2 |
| C: orlistat therapy plus low-fat diet |
74 | 52.0 ± 9.2 | 21 (28) | - | 38.8±7.0 |
Abbreviations: SD, standard deviation; FG, fasting glucose; T2DM, type 2 diabetes mellitus; BMI, body mass index; I, intervention; C, control; HbA1c, glycated hemoglobin; OGTT, oral glucose tolerance test.