Table 1. Summary of included studies.

HbA1c: glycated hemoglobin, Kcal: kilocalorie, LCD: low carbohydrate diet, LCKD: low carbohydrate ketogenic diet, LGID: low glycemic index diet, SD: standard deviation, T2DM: type two diabetes mellitus, VLCKD: very low carbohydrate ketogenic diet, mg/dl: milligram per deciliter, mmol/l: millimole per liter, n: number of patients, p: p-value

Study ID: refers to included studies [9-14]

Study ID	Design/sample	Intervention	Findings	Conclusion
Yancy et al., 2005 [9]	Single-arm 16-week interventional trial. n=28 obese diabetic patients	Patients received LCKD counseling. Target carbohydrates: <20 g/day	HbA1c decreased by 16% from 7.5 ± 1.4% to 6.3 ± 1.0% (p<0.001). Fasting serum triglycerides dropped by 42% from 2.69 ± 2.87 mmol/L to 1.57 ± 1.38 mmol/L (p=0.001)	LCKD significantly improved glycemic and lipid control. Medication discontinued in seven patients; reduced in 10.
Dashti et al., 2007 [10]	A 56-week randomized clinical trial. Sample: 64 healthy obese subject. High blood glucose n=31. Normal blood glucose n=33.	Patients received an LCKD diet. Target carbohydrates: <20 g/day. Protein: 80-100 g/day.	Fasting blood glucose level decreased significantly from 10.481 ± 3.026 mmol/L to 4.874 ± 0.556 mmol/L (p=<0.0001). Fasting serum triglycerides significantly decreased from 4.681 ± 2.468 mmol/L to 1.006 ± 0.205 mmol/L (p=<0.0001).	LCKD was very effective for improving glycemic and lipid control. Also, it helps in reducing medications in patients with type II diabetes.
Westman et al., 2008 [11]	A 24-week interventional study. Sample: 84 obese diabetic patients.	Patients received an LCKD diet. Target carbohydrates: <20 g/day (n=38). Patients received a low glycemic index diet (LGID) (n=46). Low glycemic, low calories by 500 kcal 55% of daily caloric intake from carbohydrates.	The LCKD group had a greater reduction of mean ± SD HbA1c (8.8 ± 1.8% to 7.3 ± 1.5%, p=0.009, within-group change, n=21) compared to the LGID group (8.3 ± 1.9% to 7.8 ± 2.1% p=NS, within-group change, n=29; between groups comparison p=0.03). The group that received LCKD had better results with serum triglycerides (210.4 ± 10.3 mg/dL to 142.9 ± 76.9 mg/dL) by a mean change of -67.5 as compared to the group that received LGID (167.1 ± 125.7 mg/dL to 147.8 ± 128.5 mg/dL) with a mean change of -19.3.	In the LCKD, glycemic control was greater than the LGID. Twenty of 21 (95.2%) LCKD group participants had an elimination or reduction in medication, compared with 18 of 29 (62.1%) LGID group participants (p<0.01).
Hussain et al., 2012 [12]	A 24-week diet intervention trial. Sample: 363 overweight and obese, 102 of them had diabetic patients.	Patients received LCKD and LCD and chose an LCD or LCKD counseling. Target carbohydrates: 20 g/day.	HbA1c decreased with LCKD more than LCD. Fasting serum triglycerides: decreased with LCKD more than LCD. Total cholesterol: decreased with LCKD. Blood glucose level: decreased in the two groups but LCKD had a greater effect than LCD.	LCKD had significant positive effects on serum triacylglycerol and glycemic control; there was an improvement in HbA1c.
Goday et al., 2016 [13]	A multi-centric randomized clinical trial with a duration of 4 months. Sample: 89 obese diabetic patients aged between 30 and 65 years.	Patients received LCKD and LCD. Target carbohydrates: <50 g/day.	HbA1c decreased from 6.9% to 6 % (p<0.0001) in LCKD. LCKD decreased serum triglycerides from 150.5 mg/dl to 114 mg/dl (p=0.004). Fasting glucose decreased from 136.9 mg/dl to 108,9 mg/dl (p<0.0001). Decreased oral anti-diabetic medication from 33 (73.3%) to 20 (50.0%) (p=0.0267).	LCKD is most effective in reducing body weight and improving glycemic control than a standard low-calorie diet with safety and good tolerance for T2DM patients.
Saslow et al., 2017 [14]	A 32-week randomized controlled trial. Sample: 25 obese diabetic patients, intervention group n=12, control group n=13.	Patients received VLCKD counseling. Target carbohydrates: 20-50 g/day.	HbA1c decreased in 16 weeks about -0.9% and -0.8% in 32 weeks. LCKD decreased serum triglycerides in 16 weeks about -35.5 g/dl and -60.1 g/dl in 32 weeks.	LCKD had positive effects on serum triacylglycerol and glycemic control. There was an improvement in HbA1c.