TABLE 1.
Summary of included studies related to type 2 diabetes.
| No | References | Design/sample | Intervention/diet | Duration of intervention | Major findings |
|---|---|---|---|---|---|
| 1 | Dashti et al. (2007) |
n = 64 BMI <30 Obese healthy cases with high blood sugar (31) and normal blood sugar (33) |
Low‐carb KD: 20 g/day of carb, ~80 g/day of protein | 56 weeks | ↘Bodyweight, ↘body mass index, ↘the level of blood glucose, ↘total cholesterol, ↘LDL‐cholesterol, ↘triglycerides, and ↘urea, while ↗HDL cholesterol (p < .0001) |
| 2 | Westman et al. (2008) |
n = 84 BMI 27–50 kg/m2 Obese diabetic cases |
Low‐carb KD (n = 38): 20 g/day of carb, low glycemic index (n = 46): 500 kcal less carb calories than daily carb intake |
24 weeks | ↘HbA1c, ↘fasting glucose, ↘fasting insulin, and ↘weight loss, and HDL. Diabetic drugs reduced in 95.2% of LCKD versus 62% of LGID cases (p < .01) |
| 3 | Goldstein et al. (2011) |
n = 52 BMI 30–39.9 kg/m2 Type 2 diabetic cases |
Stage 1 (4 weeks): diet with 80% of their caloric requirements based on DASH (the dietary approach to stop hypertension) Stage 2 (13 weeks): Atkins diet (25–40 g/day of carb) or standard recommended American Diabetes Association calorie‐restricted diet (g 10%–20%) of the daily energy intake from protein and the other 80% from fat Stage 3 (13–52 weeks): same diet, but the ATK and ADA groups had diets with fewer carbohydrates than the DASH diet |
12–52 weeks | ↔Weight, ↘systolic blood pressure, ↘diastolic blood pressure (mmHg), ↘HbA1c (%), ↔fasting glucose (mg/dL), ↘total cholesterol (mg/dL), ↘triglyceride (mg/dL), ↗HDL cholesterol (mg/dL), ↔microalbumin (mg/L), ↔urea (mg/dL) |
| 4 | Hussain et al. (2012) |
n = 363 BMI <25 kg/m2 Obese and overweight cases including 102 cases were type 2 diabetes |
Low‐carb diet and low‐carb KD were instructed: with initial goal of ~20 g/day of carb intake | 24 weeks | ↘Body weight, ↘blood glucose, and ↘waist circumference of the diabetic, ↘HbA1c, ↘LDL, ↘total cholesterol, ↘triglycerides, ↗ urea, and ↗ HDL of diabetic and non‐diabetic cases (p < .0001). While ↘uric acid and ↘ creatinine noticed in LCKD group |
| 5 | Wycherley et al. (2016) |
n = 115 BMI 34.6 ± 4.3 kg/m2 Obese adults with type 2 diabetes |
Low‐carb KD (57): 14% carbohydrate (<50 g/day), 28% of protein, and 58% of total fat (35% monounsaturated fat and 13% polyunsaturated fat) High‐carb diet (58): 53% of carbohydrate (emphasis on low glycemic index foods), 17% of protein, and <30% of total fat (15% monounsaturated fat and 9% polyunsaturated fat) |
52 weeks |
In both groups, ↔ HbA1c, ↔ FPG ↔ BMI, ↔ WC Compared to high‐carb, low‐carb KD group, ↔ MAGE (p = .09), ↘ CONGA‐1 (p = .003), ↘ CONGA‐4 (p = .02), ↔ time in euglycemia, ↔ time in hypoglycemia, ↘ medication (p = .02), ↘ TAG (p = .001), ↗ HDL‐c (p = .002) |
| 6 | Goday et al. (2016) |
n = 89 BMI 33.1 ± 1.6 kg/m2 Obese cases with type 2 diabetes |
Low‐carb KD (45): 600–800 kcal/day, carb <50 g/day, protein 0.8–1.2 g/kg, fat (10 g of olive oil) Hypocaloric diet (44): 500–1000 kcal, CHO 45%–60%, protein 10%–20%, fat <30% |
13 weeks | Compared to the end of stage 1, in both groups, ↘ HbA1c (p < .0001), ↔ FBG, ↔ weight, ↗ TAG (p = .027), ↘ T‐Chol (p = .038), ↗ HDL‐c (p = .0026). Decreased oral antidiabetic medication (p = .0267) |
| 7 | Saslow, Mason, et al. (2017) |
n = 25 BMI ≥25 kg/m2 Obese cases with type 2 diabetes |
Low‐carb KD (12): 25–50 g/day of carbohydrates, ~20% of calories from carbohydrates Control diet (13): More than 50% of calories from carbohydrates |
32 weeks | Compared to the control group, VLCKD had ↘ HbA1c (p = .002), ↘ weight (p < .001), ↘ TAG (p = .01), ↔ HDL‐c, ↔ LDL‐c |
| 8 | Saslow, Daubenmier, et al. (2017) |
n = 34 BMI > 25 kg/m2 Obese cases with type 2 diabetes |
Low‐carb KD (16): 20–50 g/day of carbohydrate Moderate carbohydrate, calorie‐restricted, low‐fat (MCCR) diet (18): 500 kcal reduced/day, 45%–50% of daily calories from carb, low fat |
52 weeks |
Compared to baseline, LCKD ↘ HbA1c (p < .007), ↔ fasting insulin, ↔ HOMA index ↘ medication (SU and DDP‐4 inhibitors, p = .005, metformin p = .08), ↘ weight (p = .001) |
| 9 | Hallberg et al. (2018) |
n = 349 (262 in intervention) BMI 40.4 ± 8.8 kg/m2 Obese cases with type 2 diabetes |
Restricted carb diet: >30 g/day of carb., 1.5 g/kg of daily protein intake |
52 weeks |
↘ HbA1c (p < .0001), ↘ FPG (p < .0001), ↘ fasting insulin (p < .0001), ↘ HOMA index (p < .0001), ↘ diabetes medication, except metformin (↗) and GLP‐1 (↔) ↘ weight (p < .0001), ↘ TAG (p < .0001), ↗ HDL‐c (p < .0001), ↘ LDL‐c (p < .0001), ↘ ALT (p < .0001), AST (p < .0001) |
| 10 | Barbosa‐Yañez et al. (2018) |
n = 36 BMI 35.0 ± 5.0 kg/m2 Obese cases with type 2 diabetes |
Low‐carb KD (16): ≤40 g/day of 5%–10% carb, 20%–30% protein, and 60%–70% fat Low‐fat diet (20):1000–1200 kcal/day from diet with 50% carb, 20% protein, <30% fat |
3 weeks |
Compared to baseline, in both groups ↘ HbA1c (p < .001), ↘ weight (p < .001), ↘ total body fat (p = .001), ↘ T‐cholesterol (p ≤ .001), ↘ LDL‐c (p ≤ .004), ↘ TAG in both groups (p ≤ .042), ↘ visceral adipose tissue (p = .024), (p < .001) for LCKD and LFD, respectively |
| 11 | Myette‐Côté et al. (2018) |
n = 11 BMI 34.0 ± 8.0 kg/m2 Obese cases with type 2 diabetes |
1. Low‐fat low glycemic index diet: ~55% CHO, 25% protein, 20% fat 2. Very low‐carb KD: <10% CHO, 25% protein, ~65% fat 3. Very low‐carb KD+ exercise: <10% CHO, 25% protein, ~65% fat +15 min of walking beginning 30 min after each meal |
4 days |
Compared to baseline in three groups: ↔ Glucose, ↔ triglyceride, and ↔ insulin level. Compared to baseline: ↘ proinsulin for VLCKD (p = .001) and VLCKD + exercise (p = .005), but ↔ proinsulin for low‐fat low glycemic index diet Compared to low‐fat low glycemic index diet ↘ mean glucose in the VLCKD with or without exercise (p ≤ .001), ↔ time in hypoglycemia |
| 12 | Romano et al. (2019) |
n = 20 BMI 37.1 ± 6.8 kg/m2 Obese cases with type 2 diabetes |
Low‐carb KD: 10%–20% of carbohydrate (≤25 g/day), 60%–70% protein, 25%–30% fat | 2 weeks | ↘ HbA1c (p < .0001), ↘ HOMA index (p < .0001), ↘ Weight (p < .001), ↘ BMI (p < .001), ↘ WC (p < .001), ↘ segmental (p < .001), whole fat mass (p < .001), ↘ AST (p < .0001), ↘ ALT (p < .0001) |
| 13 | Walton et al. (2019) |
n = 11 BMI 36.3 ± 1.4 kg/m2 Obese cases with type 2 diabetes |
Low‐carb KD: ~5% (≤30 g/day) of carbohydrate, ~20%–25% of protein, ~70%–75% of fat |
13 weeks |
↘HbA1c (p < .0001), ↘weight (p < .0001), ↗ HDL‐c (p < .005), ↘TAG (p < .005), ↘TAG: HDL‐c ratio (p < .005), ↔ LDL‐c ↔ AST, ↔ ALT |
| 14 | Albanese et al. (2019) | 72 patients (60 F/12 M) | Very‐low‐calorie keto diet (VLCKD) | 3 weeks | Total weight loss better in VLCKD than in VLCD group (5.8 ± 2.4 vs. 4.8 ± 2.5 kg, p = .008). Surgical outcomes: mean operative time slightly shorter in VLCKD group; percentage of patients requiring a longer‐than‐anticipated hospital stay lower in VLCKD group; lower drainage output and higher post‐operative hemoglobin levels in VLCKD group |
Abbreviations: CONGA‐1, continuous overall net glycemic action of observations 1 h apart; CONGA‐4, continuous overall net glycemic action of observations 4 h apart. T‐Chol, total cholesterol; FBG, fasting blood glucose; HDL‐c, high‐density lipoprotein cholesterol; HOMA, Homeostasis Model Assessment; KD, ketogenic diet; LDL‐c, low‐density lipoprotein cholesterol; SU, sulfonylurea; T2D, type 2 diabetes mellitus; TAG, triacylglycerol; TMAGE, mean amplitude of glycemic excursion; WC, waist circumference.