TABLE 1.
Characteristics of included trials
| Authors, year, country | Study design | Sample size | Study duration (weeks) | Age (years) | BMI (kg/m2) | Sex (% female) | Population | Intervention diet | Control diet | Outcomes | Support | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Randomized Completed |
BW | BMI | HbA1c | Blood pressure | Blood lipids | ||||||||||
|
Barnard et al., 2005 18 USA |
RCT Parallel |
64 (IG: 32, CG: 32) 59 (IG: 29, CG: 30) |
14 |
IG: 57.4 [47–71] CG: 55.6 [44–73] |
IG: 33.6 ± 5.2 CG: 32.6 ± 3.3 |
100% | Overweight |
Low‐fat vegan diet Ad libitum |
Diet based on the National Cholesterol Education Program Ad libitum |
✓ | ✓ |
Both groups: No meals provided. Weekly 1‐h meetings (nutrition and cooking instruction + group discussions) |
|||
|
Barnard et al., 2006 20 USA |
RCT Parallel |
99 (IG: 49, CG: 50) 99 (IG: 49, CG: 50) |
22 |
IG: 56.7 [35–82] CG: 54.6 [27–80] |
IG: 33.9 ± 7.8 CG: 34.4 ± 7.3 |
IG: 55% CG: 66% |
T2D |
Low‐fat vegan diet + B12 Ad libitum |
Diet based on the American Diabetes Association guidelines + B12 Energy deficit: 500–1000 kcal/day |
✓ | ✓ | ✓ | ✓ | ✓ |
Both groups: No meals provided. Weekly 1‐h meetings (nutrition and cooking instruction). Continuous dietary counseling |
|
Barnard et al., 2018 30 USA |
RCT Parallel |
45 (IG: 21, CG: 24) 40 (IG: 19, CG: 19) |
20 |
IG: 61 [41–79] CG: 61 [30–75] |
IG: 34.9 ± 1.5 a CG: 33.0 ± 1.3 a |
IG: 62% CG: 46% |
T2D |
Low‐fat vegan diet + B12 Ad libitum |
Portion‐controlled diet + B12 Energy deficit: 500 kcal/day |
✓ | ✓ | ✓ | ✓ | ✓ |
Both groups: No meals provided. Weekly 1‐h meetings (nutrition and cooking instruction + support) |
|
Barnard et al., 2021 50 USA |
RCT Cross‐over |
62 52 |
2 × 26 |
IG first: 58.3 ± 8.4 a CG first: 56.6 ± 10.9 a |
IG first: 33.7 ± 3.4 a CG first: 34.3 ± 2.7 a |
77% | Overweight |
Low‐fat vegan diet + B12 Ad libitum |
Mediterranean diet Ad libitum |
✓ | ✓ | ✓ | ✓ | ✓ |
Both groups: No meals provided. Weekly meetings (nutrition and cooking instruction + support) |
|
Bunner et al., 2015 33 USA |
RCT Parallel Pilot study |
35 (IG: 17, CG: 18) 34 (IG: 17, CG: 17) |
20 |
IG: 57 ± 6 CG: 58 ± 6 |
IG: 36 ± 6 CG: 36 ± 7 |
IG: 65% CG: 47% |
T2D |
Low‐fat vegan diet + B12 Ad libitum |
No dietary changes + B12 Ad libitum |
✓ | ✓ | ✓ | ✓ | ✓ |
Intervention group: No meals provided. Weekly meetings (education + social support) |
|
Jenkins et al., 2014 51 Canada |
RCT Parallel |
39 (IG: 20, CG: 19) 23 (IG: 10, CG: 13) |
26 |
IG: 57.6 ± 1.4 a CG: 55.3 ± 1.8 a |
IG: 31.1 (29.8–32.4) CG: 31.1 (29.9–32.4) |
IG: 55% CG: 68% |
Overweight |
Low‐carbohydrate vegan diet 40% energy reduction |
High‐carbohydrate lacto‐ovo vegetarian diet 40% energy reduction |
✓ | ✓ | ✓ | ✓ | ✓ |
Both groups: No meals provided. Continuous dietary counseling. Menu plans provided |
|
Kahleova et al., 2020 17 USA |
RCT Parallel |
244 (IG: 122, CG: 122) 223 (IG: 117, CG: 106) |
16 |
IG: 53 ± 10 CG: 57 ± 13 |
IG: 33.3 ± 3.8 CG: 33.6 ± 3.7 |
IG: 86% CG: 87% |
Overweight |
Low‐fat vegan diet + B12 Ad libitum |
No dietary changes + B12 Ad libitum |
✓ | ✓ | ✓ | ✓ |
Intervention group: No meals provided. Weekly meetings (nutrition and cooking instruction) |
|
|
Lee et al., 2016 31 Korea |
RCT Parallel |
106 (IG: 53, CG: 53) 93 (IG: 46, CG: 47) |
12 |
IG: 57.5 ± 7.7 CG: 58.3 ± 7.0 |
IG: 23.9 ± 3.4 CG: 23.1 ± 2.4 |
IG: 87% CG: 75% |
T2D |
Vegan diet Ad libitum |
Korean Diabetes Association Diet Energy restricted (not specified) |
✓ | ✓ | ✓ | ✓ |
Both groups: No meals provided. Weeks 0 and 4 (nutrition education + instruction). Weekly telephone call |
|
|
Nicholson et al., 1999 32 USA |
RCT Parallel Pilot study |
13 (IG: 7, CG: 6) 11 (IG: 7, CG: 4) |
12 |
IG: 51 [34–62] CG: 60 [51–74] |
NA |
IG: 42% CG: 50% |
T2D |
Low‐fat vegan diet Ad libitum |
Low‐fat diet Ad libitum |
✓ | ✓ | ✓ | ✓ |
Both groups: Lunch and dinner provided. Twice‐weekly meetings (cooking instruction + education + support) |
|
|
Turner‐McGrievy et al., 2015 40 USA |
RCT 5‐arm b |
24 (IG: 12, CG: 12) 21 (IG: 12, CG: 9) |
26 |
IG: 48.2 ± 7.4 CG: 51.0 ± 8.6 |
IG: 32.5 ± 5.2 CG: 36.3 ± 5.5 |
IG: 67% CG: 75% |
Overweight |
Low‐fat vegan diet + B12 Ad libitum |
Healthy omnivores diet + B12 Ad libitum |
✓ | ✓ |
Intervention group: No meals provided. Weekly 1‐h meetings for 8 weeks Control group: No meals provided. Meetings at Weeks 0, 4, and 8. Weekly email (dietary information) |
|||
|
Wright et al., 2017 49 New Zealand |
RCT Parallel |
65 (IG: 33, CG: 32) 49 (IG: 25, CG: 24) |
26 |
IG: 56 ± 9.9 CG: 56 ± 9.5 |
IG: 34.5 (32.9–36.1) CG: 34.2 (31.9–36.5) |
IG: 67% CG: 53% |
Overweight (14% with T2D) |
Low‐fat vegan diet + B12 Ad libitum |
No dietary changes Ad libitum |
✓ | ✓ | ✓ | ✓ | ✓ |
Intervention group: Twice‐weekly 2‐h meetings for 12 weeks (cooking instruction + education + discussion) |
Note: Data depicted as mean ± standard deviation or [range] or (95% confidence interval).
Abbreviations: BMI, body mass index; BW, body weight; CG, control group; HbA1c, glycated hemoglobin; IG, intervention group; NA, not applicable; RCT, randomized controlled trial; T2D, type 2 diabetes.
Indicates mean ± standard error.
Only two groups of the five‐arm study are presented in this review.