Table 1.
Characteristics of studies included.
| First Author, Year | Design | Study Population | Intervention | Control | Duration of Intervention | ITT |
|---|---|---|---|---|---|---|
| Moreno, 2016 [26] | An open, prospective, randomized, controlled nutritional intervention clinical trial. | Initial sample Intervention: 22 Control: 23 Mean age ± SD: Intervention: 44.6 ± 7.8 Control: 45.6 ± 9.6 Percentage of women Intervention: 77.3 Control: 95.7 Madrid, Spain |
Very low-calorie ketogenic diet (VLCKD): Pronokal method. Three stages. Active stage: 600–800 kcal/day CHO: <50 g/day Protein: 0.80–1.2 g per kilo of ideal weight (only high biological value). In reeducation stage: ketone bodies were evaluated by a physician, and a low-calorie diet was begun, with a progressive incorporation of food. In maintenance: progression to a balanced diet plan. |
Low-Calorie Diet (LCD) 10% of the total calories calculated per individual: 1440–1800 kcal/day. Lipids: 25–35% CHO: 45–55% Protein: 15–25% Fiber: 20–40 g/day |
24 months | Yes43% total dropout (not specified and cannot be deduced per group) |
| Moreno, 2014 [22] | An open, prospective, randomized, controlled nutritional intervention clinical trial. | Initial sample Intervention: 27 Control: 26 Mean age ± SD: Intervention: 44.4 ± 8.6 Control: 46.3 ± 9.3 Percentage of women: Intervention: 81.4 Control: 96.1 Madrid, Spain |
VLCKD: Pronokal method. | LCD: 10% of the total calories calculated per individual | 12 months | Yes Dropout rate Intervention: 30.8% Control: 35.0% |
| Gutiérrez-Repiso, 2019 [27] | A single-blind, randomized, controlled nutritional intervention clinical trial. | Initial sample Intervention: 15 Control: 9 Mean age ± SD: Intervention: 48.67 ± 9.16 Control: 38.22 ± 11.27 Percentage of women: Intervention: 81.4 Control: 66.6 Málaga, Spain |
VLCKD: Pronokal method, plus symbiotic supplements in the form of capsules (2 months) + LCD for 2 months + symbiotics. |
Placebo | 4 months | Unclear Dropout rate Not reported and cannot be deduced |
| Westman, 2006 [28] | Two-armed randomized trial | Sample: Intervention: 59 Control: 60 Mean age ± SD: Intervention: 44.4 ± 10.1 Control: 45.6 ± 9.0 Percentage of women: Intervention: 75% Control: 78% North Carolina, USA |
Low-carbohydrate, ketogenic diet (initially <20 g of carbohydrates/day) plus nutritional supplements |
Low-fat, low-calorie diet | 6 months | Unclear Dropout rate: 0.84% total dropout (not specified and cannot be deduced per group) However, the authors consider the initial and final sample to be the same number of participants. |
| Tay, 2018 [30] | Two-armed randomized trial. | Initial sample Intervention: 58 Control: 57 Mean age ± SD: Intervention: 58 Control: 58 Percentage of women: Intervention: 64% Control: 54% Adelaide, Australia |
Low-carbohydrate diet, high in unsaturated fats and low in saturated fats: CHO: 14% (<50 g/day) Protein: 28% Lipids: 58% (35% monounsaturated and 13% polyunsaturated fats) |
CHO: 53% (processed foods are discouraged). Protein: 17% Lipids: 30% (15% monounsaturated and 9% polyunsaturated fats) |
24 months | Yes Dropout rate: Intervention: 13.8% Control: 15.8% |
| Veum, 2017 [24] | Two-armed randomized trial. | Initial sample Intervention: 18 Control: 20 Mean age ± SD: Intervention: 40.2 ± 4.5 Control: 40.3 ± 5.5 The study only considered men. Bergen, Norway |
High-fat, low-carbohydrate diet: Lipids: 73% CHO: 10% |
Low-fat, high-carbohydrate diet: Lipids: 30% CHO: 53% |
12 weeks (3 months) | Yes (per protocol principle was also reported) Dropout rate: 17.4% total dropout (not specified and cannot be deduced per group) |
| Tay, 2014 [31] | Two-armed parallel randomized trial. | Initial sample Intervention: 58 Control: 57 Mean age ± SD: Intervention: 58 ± 7 Control: 58 ± 7 Percentage of women: Intervention: 36.2% Control: 49.1% Adelaide, Australia |
Low-carbohydrate diet, high in unsaturated fats and low in saturated fats: CHO: 14% (<50 g/day) Protein: 28% Lipids: 58% (35% monounsaturated and 13% polyunsaturated fats) |
CHO: 53% (processed foods are discouraged). Protein: 17% Lipids: 30% (15% monounsaturated and 9% polyunsaturated fats) Saturated fatty acids were restricted to 10% in both groups. |
24 weeks (6 months) | Unclear Dropout rate: Intervention: 21% Control: 18% |
| Haufe, 2011 [32] | Two-armed randomized trial. | Initial sample Intervention: 84 Control: 86 Mean age: Intervention: 43.2 Control: 45.1 Percentage of women: Intervention: 84.6% Control: 80.0% Germany |
1200 cal/day diet CHO: 90 g/day Protein: 0.80 g-Kg/day Lipids: >30% |
Control diet: Protein: 0.80 g-Kg/day Lipids: 20% |
6 months | Yes Dropout rate: Intervention: 38.1% Control: 41.8% |
| Iqbal, 2010 [23] | Randomized controlled trial | Initial sample Intervention: 70 Control: 74 Mean age: Intervention: 60.0 ± 8.9 Control: 60.0 ± 9.5 Percentage of women: Intervention: 15.7% Control: 5.4% Philadelphia, USA |
Low-carbohydrate (high-fat) diet: CHO: <30 g/day Subjects were advised to consume whole and high fiber content foods. Fat intake was not restricted (subjects were advised to consume healthy sources of fat). |
Low-fat control diet, <30% of calories/day. Subjects were encouraged to consume healthy fats: <7% of total calories from saturated fat, <300 mg of cholesterol, and to increase intake of fruits and vegetables. |
24 months | Yes Dropout rate: Intervention: 60.0% Control: 46.0% |
| Yancy, 2004 [29] | Two-armed randomized trial | Initial sample Intervention: 60 Control: 60 Mean age: Intervention: 45.6 ± 9.0 Control: 44.2 ± 10.0 Percentage of women: Intervention: 78% Control: 75% North Carolina, USA |
Low-carbohydrate diet CHO: <20 g/day (in the beginning) + nutritional supplements + exercise recommendation + group meetings (4 times/month in the beginning and then monthly for three months) |
Low-fat diet: Lipids: <30% of energy from fat, <300 mg cholesterol/day, and deficit of 500 to 1000 cal/day + recommendation of exercise + group meetings (4 times/month in the beginning and then monthly for three months). |
24 weeks | Unclear Dropout rate: Intervention: 24.0% Control: 43.0% |
Abbreviations: ITT, intention to treat; CHO, carbohydrates; VLCKD, Very low-calorie ketogenic diet; LCD, Low-Calorie Diet.