Table 3.
Summary findings from randomized control trials based on the impact of soy on obesity and satiety.
| Study | Sample Size & Population | Duration | Treatment | Dose; Format | Results | Conclusions |
|---|---|---|---|---|---|---|
| [146] | 25 abdominally obese men and women | 12 weeks, parallel RCT | Soy protein meal replacement | 4 replacement meals/day: 44 g soy protein, 60–135 mg isoflavones/day | No significant variations in body composition (including weight, BMI, % fat and % lean mass) or cardiometabolic risk factors were observed in the soy replacement meal compared to control | Soy protein affects weight loss to same extent as other proteins |
| [28] | 39 overweight and obese adults | Daily breakfast for 12 weeks | Soy fiber supplemented biscuits | 100 g soy fiber/day | LDL-C, TC and BMI decreased after 12 weeks (p < 0.05) | Soy fiber supplementation may help in weight management and lowering cholesterol levels |
| [144] | 45 patients with non-alcoholic fatty liver disease | 8 weeks, parallel RCT | 3 diets: low-calorie; low- calorie, low carbohydrate; low-calorie, low soy diet | 30 g soy nuts containing: 7 g fat, 9 g fiber, 11.3 g protein, 10 mg sodium, 102 mg phytoestrogens | Soy group had greatest decline in serum liver enzymes and fibrinogens, and malondialdehyde. There were no changes in BMI or weight between the two groups | Soy may mitigate inflammation when combined with a low-calorie diet, but may not affect weight loss in those with non-alcoholic fatty liver disease. |
| [158] | 11 overweight and obese men | 1 day, parallel RCT | Soy protein breakfast meal replacement, followed by standardized lunch 4 h later | Meal replacement, containing 28.7 soy protein (34.6 g total protein), 19.8 g carbohydrate | Meal replacement group had lower glucose levels, glucose and insulin AUC, ghrelin concentrations following breakfast; Fat oxidation was lower after lunch | Soy protein could have a potential hypoglycemic effect, as well as mediating metabolic risk factors and improving weight management |
| [150] | 380 women, BMI of 30–40 kg/m2, 76 of whom took the soy meal replacement | 12 months, with meal replacement taken for a maximum of 3 months (most did so during first 3 months of study) | Soy-based meal replacement (in addition to baseline lifestyle program administered to both control and treated groups) | Soy-yogurt-honey product: 83% soy-protein isolate, 17% milk protein | Weight loss was greater in meal replacement group (p = 0.1); health-related quality of life scores also increased more compared to control | Soy protein consumption may enhance weight loss when combined with a lifestyle intervention program focusing on diet and physical activity |
| [149] | 64 overweight/obese subjects | 12 weeks, parallel RCT | Black soy peptide (BSP) supplementation | 4.5 g/day in tablet form | After 12 weeks, BSP group had statistically significant decrease in body weight, body fat mass, body fat % and plasma leptin (vs. no change in placebo); no change in inflammatory markers or lipid profiles between groups | Black soy peptide seems to have a role in weight and fat mass regulation in overweight subjects, perhaps by altering leptin levels |
| [156] | 116 healthy men and women | 6 weeks, parallel RCT | Soy muffins (vs. control wheat muffins) | 12.5 g soy protein muffin; 2 muffins/day | Higher fullness scores in soy muffin group on a Visual Analog Scale (p = 0.002) vs. control group | Replacing wheat flour with soy flour may increase perceived satiety |
| [145] | 38 obese men and women | 8 weeks, parallel RCT | Whole soy powder bar (vs. wheat control) | 1 bar eaten 1–2 h before dinner daily | Compared to control, soy group had lower BMI, waist circumference and body fat % (p < 0.05). No significant differences in weight loss, TC, LDL = C, or insulin were found between the two groups | Whole soy can complement the benefits of a weight-loss program; whether it does so by mediating glycemic response remains unclear based on this study. |
| [147] | 48 obese Japanese adults | 20 weeks, parallel RCT | Soy protein | Soy protein intervention containing 12 g soy protein, 9 g milk protein; consumed at breakfast | Visceral and subcutaneous fat, body weight and BMI decreased significantly after 20 weeks of milk protein ingestion, but not after ingestion of soy protein containing milk protein | Milk protein has a more substantial impact on markers of weight loss compared to a combination of milk and soy protein |
AUC = area under blood glucose response curve; BMI = body mass index; LDL-C = low density lipoprotein cholesterol; RCT = randomized control trial; TC = total cholesterol.