Microbiome-Targeted Therapies as an Adjunct to Traditional Weight Loss Interventions: A Systematic Review and Meta-Analysis

Figures & data

Figure 1 Flowchart of study selection. Preferred Reporting in Systematic Reviews and Meta-analyses (PRISMA) flowchart showing the study selection process.

Table 1 Characteristics of Included Studies

First Author, Year, Reference, Country	Study Design	Study Duration and Stages	Participant Characteristics (mean ± SD)	Microbiome-Targeted Therapy and Details	Dietary/Exercise Intervention	Groups	Significant Anthropometric Outcomes (at the End of Treatment)
Prebiotics
Vaghef-Mehrabany 2019^Citation61 Iran	Randomized, double-blind, placebo-controlled study	8 weeks	45 obese women with the major depressive disorder; Age: 38.7 ± 7.8 years; BMI: 34.02 ± 3.9 kg/m^2; 100% female; Attrition: 27.4%	Prebiotic: Inulin (10 g/day sachet dissolved in water)	25% calorie-restricted diet with meal plan, composed of 55%/ 15%/ 30% carbohydrate/ protein/ fat	A) Prebiotic + hypocaloric diet (n=22) B) Placebo + hypocaloric diet (n=23)	Reduced ***BW, ***BMI, ***WC, and ***HC in both groups, but NS differences between groups. Reduced ***FM in group A only, but NS difference between groups.
Probiotics
Banach 2020^Citation34 Poland	Randomized, single-blind, placebo-controlled study	12 weeks	54 healthy overweight and obese adults; Age: 34.5 ± 10.0 years; BMI: 34.9 ± 3.9 kg/m^2; 65% female; Attrition: 27.4%	Probiotic: 250 g/day yogurt containing Lactobacillus acidophilus LA-5 and Bifidobacterium lactis BB-12	Individualized weight loss program with hypocaloric diet (500–800 Kcal/day reduction; 45–60%/ 15–25%/ 25–35% carbohydrate/ protein/ fat) + 150 min of moderate or 75 min of high-intensity exercise per week + behavioural aspects, such as goal setting	A) Probiotic + weight loss program (n=27) B) Weight loss program only (n=27)	Reduced *BW and *FM in both groups, but NS difference between groups.
Doria 2013^Citation44 Italy	Randomized, double-blind, placebo-controlled study	90 days (measurements taken at 30, 60, and 90 days)	40 healthy slightly overweight women; Age: 41.4 ± 7.8 years; BMI: not given; 100% female; Attrition: 0%	Probiotic: 25 mL of dietary supplement containing Lactobacillus casei (7.5 x 10^8), Lactobacillus acidophilus (7.5 x 10^8) and other nutrients (phloridzin, isoflavones (puerarin 67%, daidzin 0.5%, daidzein 1.6%, genistein 0.4%)	Hypocaloric diet (300 Kcal/day reduction)	A) Probiotic + diet (n=20) B) Placebo + diet (n=20)	Greater reductions in **BW, **FM, ***WC, ***TC, and **BC in group A compared with group B.
Gomes 2015^Citation42 Brazil	Randomized, double-blind, placebo- controlled study	8 weeks	43 healthy overweight or obese adults; Age: 20–59 years; BMI: 32.5 ± 4.4 kg/m^2; 100% female; Attrition: 28.3%	Probiotic: 4 sachets daily, each containing Lactobacillus acidophilus LA-14, Lactobacillus casei LC-11, Lactococcus lactis LL-23, Bifidobacterium bifidum BB-06, and Bifidobacterium lactis BL-4 (2 x 10^10 CFU/day total)	Normocaloric diet (25–30 kcal/kg; energy intake according to expected BW for height) + maintenance of pre-trial physical activity	A) Probiotic sachets + diet B) Placebo sachets + diet	Greater reduction in *WC in group A compared with B. Reduced *FM in group A only, but NS difference between groups.
Kim et al 2018^Citation35 Korea	Randomized, double-blind, placebo- controlled study	12 weeks	90 healthy overweight and obese adults; Age: 38.4 ± 9.8 years; BMI: 28.4 ± 2.5 kg/m^2; 70% female; Attrition: 14.4%	Probiotic: 1600 mg/day of low dose (10^9 CFU) or high dose (10^10 CFU) Lactobacillus gasseri BNR17 (BNR-H)	Hypocaloric diet (200 kcal/day reduction) + increased energy expenditure (100 kcal/day)	A) Low-dose probiotic (10^9 CFU) + diet/exercise plan (n=30) B) High dose probiotic (10^10 CFU) + diet/exercise plan (n=30) C) Placebo + diet/exercise plan (n=30)	Greater reduction in *FM in groups A and B compared with C. Reduced *WC in groups A & B, but NS difference between groups.
Madjd 2016^Citation37 Iran	Randomized, double-blind, controlled study	12 weeks	89 healthy overweight and obese women; Age: 32.0 ± 6.8 years; BMI: 32.1 ± 3.6 kg/m^2; 100% female; Attrition: 9%	Probiotic: 400 g/day of probiotic yogurt containing Lactobacillus acidophilus LA5 and Bifidobacterium lactis BB12 (1 x 10^7 CFU)	Hypocaloric diet (500–1000 kcal/day reduction) + physical activity (gradual increase to 60 min of moderate exercise 5 days/ week)	A) Probiotic yogurt + hypocaloric diet + exercise (n=44) B) Yogurt (no probiotic) + hypocaloric diet + exercise (n=45)	Reduced **BM, **BMI, and **WC in both groups, but NS difference between groups.
Narmaki^Citation62 Iran	Randomized, double-blind, placebo-controlled study	2 phases of 6 weeks: Phase 1: reduced calorie diet only Phase 2: reduced calorie diet + capsules	62 obese women with food addiction; Age: 33.2 ± 6.5 years; BMI: 34.4 ± 2.9 kg/m^2; 100% female; Attrition: 8%	Probiotic: Capsules containing 6 species: Lactobacillus acidophilus (1.8 x 10^9 CFU/capsule), Bifidobacterium bifidum (1.8 x 10^9 CFU/capsule), Bifidobacterium lactis (1.8 x 10^9 CFU/capsule) Bifidobacterium longum (1.8 x 10^9 CFU/capsule), Lactobacillus rhamnosus (1 x 10^9 CFU/capsule), and Lactobacillus reuteri (1 x 10^9 CFU/capsule)	Personalized hypocaloric diet (300–500 Kcal/day reduction; approx. 55%/ 15%/30% carbohydrate/ protein/ fat)	A) Probiotic + hypocaloric diet (n=31) B) Placebo + hypocaloric diet (n=31)	Reduced ***BW, ***BMI, ***WC, ***WHR, ***BF and ***TF in group A compared with group B.
Omar 2013^Citation63 Canada	Randomized, double-blind, placebo- controlled, cross-over study	3 Phase of 43 days, separated by a washout period of 6 weeks	28 healthy overweight and obese adults; Age: 46.3 ± 2.4 years; BMI: 31.6 ± 0.7 kg/m^2; 64% female; Attrition: not given	Probiotic: 100 g/day yogurt containing 10 g of Lactobacillus amylovorus (1.39 x 10^9 CFU) and 10 g of Lactobacillus fermentum (1.08 x 10^9 CFU)	Hypocaloric diet containing 50%/ 15%/ 35% carbohydrate/ protein/ fat	A) Yogurt containing Lactobacillus fermentum + hypocaloric diet (n=14) B) Yogurt containing Lactobacillus amylovorus + hypocaloric diet (n=12) C) Regular yogurt + hypocaloric diet (n=12)	Reduced *FM in all groups, but NS difference between groups.
Razmpoosh 2019^Citation45 Iran	Randomized controlled study	8 weeks	65 overweight and obese women; Age: 36.5 ± 8.0 years; BMI: 31.5 ± 4.6 kg/m^2; 100% female; Attrition: 7%	Probiotic: 50g/day pasteurized liquid probiotic Kashk containing Lactobacillus acidophilus La5 (1.85 x 10^6 CFU/g) and Bifidobacterium lactis Bb12 (1.79 x 10^6 CFU/g)	Hypocaloric diet (500 kcal/day reduction; approx. 58%/ 15%/ 27% carbohydrate/ protein/ fat)	A) Probiotic + hypocaloric diet (n=32) B) Hypocaloric diet only (n=33)	Reduced **BW, **BMI, **BFM, **BFP, and *WC in group A compared with group B. NS between-group differences in FFM.
Sharafedtinov 2013^Citation64 Estonia	Randomized, parallel, double-blind, placebo- controlled pilot study	3 weeks	36 obese adults, with metabolic syndrome; Age: 51.9 ± 11.2 years; BMI: 37.2 ± 4.2 kg/m^2; 68% female; Attrition: 10%	Probiotic: 50 g/day of probiotic cheese containing Lactobacillus plantarum TENSIA	Hypocaloric diet (1512 kcal/day)	A) Probiotic cheese + hypocaloric diet (n=25) B) Regular cheese (no probiotic) + hypocaloric diet (n=11)	Reduced *BMI and *WHR in group A compared with group B. NS between-group differences in BW and FM.
Zarrati 2018^Citation36 Iran	Randomized, double-blind, placebo-controlled study	8 weeks	56 obese or overweight individuals; Age: 36.1 ± 9.0 years; BMI: 32.1 ± 4.4 kg/m^2; 70% female; Attrition: 6.7%	Probiotic: 200 g/day yogurt containing Lactobacillus acidophilus LA5, Lactobacillus casei DN001, and Bifidobacterium lactis Bb12 (1 x 10^8 CFU/g each)	Hypocaloric diet (500 kcal/day reduction; 55–60%/ 12–15%/ 30–35% carbohydrate/ protein/ fat) + 30–45 minutes walking 3–5 times/week	A) Probiotic + hypocaloric diet + exercise (n=26) B) Regular yogurt + hypocaloric diet + exercise (n=30)	Reduced **BFP in group A compared with group B. NS between-group differences in BW, BMI, or WC.
Zarrati 2014^Citation65 Iran	Randomized, double-blind, controlled study	8 weeks	75 healthy overweight and obese adults; Age: 35.7 ± 8.9 years; BMI: 33.2 ± 5.7 kg/m^2; 68% female; Attrition: 0%	Probiotic: 200 g/day probiotic yogurt containing Lactobacillus acidophilus La5 (1 x 10^7 CFU/mL), Bifidobacterium BB12, and Lactobacillus casei DN001 (1 x 10^7 CFU/mL)	Hypocaloric diet (details not provided)	A) Probiotic yogurt + hypocaloric diet (n=25) B) Probiotic yogurt only (n=25) C) Regular yogurt + hypocaloric diet (n=25)	Reduced ***BW, ***BMI, and ***WC in group A compared with group B and group C compared with group B.
Synbiotics
Eslamparast 2014^Citation38 Iran	Randomized, double-blind, placebo-controlled pilot study	28 weeks	38 adults with metabolic syndrome; Age: 46.8 ± 9.5 years; BMI: 31.8 ± 2.5 kg/m^2; 60.5% female; Attrition: 0%	Probiotic: Capsule containing 2×10^8 CFU of seven strains (Lactobacillus casei, Lactobacillus rhamnosus, Streptococcus thermophilus, Bifidobacterium breve, Lactobacillus acidophilus, Bifidobacterium longum and Lactobacillus bulgaricus) Prebiotic: 250mg FOS	Hypocaloric diet (500–1000 kcal reduction) + 20–30 min of high-intensity exercise 3–4 day/week (or more)	A) Synbiotic capsule + diet + exercise (n=19) B) Placebo capsule + diet + exercise (n=19)	NS within- or between-group differences in BMI and WC.
Eslamparast 2014b^Citation39 Iran	Randomized, double-blind, placebo-controlled pilot study	28 weeks	52 adults with non-alcoholic fatty liver disease; Age: 46.0 ± 9.2 years; BMI: 31.7 ± 2.4 kg/m^2; 92.6% female; Attrition: 7.7%	Probiotic: Capsule containing 2×10^8 CFU of seven strains (Lactobacillus casei, Lactobacillus rhamnosus, Streptococcus thermophilus, Bifidobacterium breve, Lactobacillus acidophilus, Bifidobacterium longum and Lactobacillus bulgaricus) Prebiotic: 250mg FOS	Hypocaloric diet (500–1000 kcal reduction) + 20–30 min of high-intensity exercise 3–4 day/week (or more)	A) Synbiotic capsule + diet + exercise (n=26) B) Placebo capsule + diet + exercise (n=26)	Reduced *BMI and *WHR in both groups, but NS differences between groups.
Ferolla 2016^Citation66 Brazil	Randomized, controlled, single-blind study	3 months	50 adults with non-alcoholic fatty liver disease; Age: median=57.3 years BMI: 32.5 ± 4.0 kg/m^2; 76% female; Attrition: 0%	Probiotic: 2 capsules of Lactobacillus reuteri (1 x 10^8 CFU) Prebiotic: 4g partially hydrolyzed guar gum and inulin	Hypocaloric diet (1500/1800 kcal for women/men – a 500–1000 kcal reduction)	A) Synbiotic capsule + diet (n=27) B) Placebo capsule + diet (n=23)	Reduced *BW, *BMI, and **WC in Group A but not group B.
Gutiérrez-Repiso 2019^Citation67 Spain	Randomized, single-blind, parallel study	2 x 2-month stages: Phase 1: 2 months very-low-calorie diet Phase 2: 2 months of a low-calorie diet	33 obese patients; Age: 45.4 ± 10.4 years; BMI: 32.9 ± 1.6 kg/m^2; 61% female; Attrition: not given	Phase 1 Probiotic: Bifidobacterium lactis, Lactobacillus rhamnosus, Bifidobacterium longum ES1 Prebiotic: Prebiotic fibre (unspecified) Phase 2 Probiotic: Bifidobacterium lactis Prebiotic: prebiotic fibre (unspecified)	Phase 1: Very-low-calorie Ketogenic Diet (PnK method, 600–800 kcal/day) Phase 2: low-calorie diet (800–1500 kcal/day)	A) Synbiotics during both phases (n=15) B) Placebo during very-low-calorie diet phase and synbiotic during low-calorie-diet phase (n=9) C) Placebo during both phases (n=9)	Reduced *BW in group B compared with group A.
Janczy 2020^Citation41 Poland	Randomized, single-blinded study	12 weeks	56 obese patients; Age: 37.2 ± 15.6 years; BMI: 33.8 ± 7.0 kg/m^2; 75% female; Attrition: 5.1%	Probiotic: Probiotic capsules (Bifidobacterium lactis ≥2.8 x 10^8, Lactobacillus acidophilus ≥1.2 x 10^8, Lactobacillus paracasei ≥0.9 x 10^8, Lactobacillus plantarum ≥1.1 x 10^8 Lactobacillus salivarius ≥0.9 x 10^8, Lactobacillus lactis ≥1.1 x 10^8) Prebiotic: 9.6 g FOS, 110.4 g inulin	Hypocaloric diet (500 kcal reduction; 45–55%/ 20–25%/ 25–30% carbohydrate/ protein/ fat + maintenance of pre-trial physical activity	A) Synbiotic + hypocaloric diet (n=36) B) Placebo + hypocaloric diet (n=20)	Reduced ***BW, ***BMI, and ***FM in both groups, but NS difference between groups.
Malaguarnera 2012^Citation68 Italy	Randomized, parallel, double-blind, placebo-controlled study	6 months	66 males and females with excess weight and non-alcoholic fatty liver disease; Age: 46.8 ± 5.5 years; BMI: 27.3 ± 1.3 kg/m^2; 50% female; Attrition: 0%	Probiotic: Bifidobacterium longum W11 (5 x 10^9 CFU) Prebiotic: 2.5 g FOS	Lifestyle modification program, including mild physical training + 1600 kcal/day diet	A) Synbiotic + lifestyle modification (n=34) B) Lifestyle modification only (n=32)	Reduced *BMI in both groups but NS difference between groups.
Mohammadi-Sartang 2019^Citation40 Iran	Randomized, parallel, double-blinded study	10 weeks	90 overweight or obese adults with metabolic syndrome; Age: 45.5 ± 8.8 years; BMI: 30.4 ± 2.4 kg/m^2; 59% female; Attrition: 3.3%	Probiotic: Fortified yogurt containing Bifidobacterium lactis Bb-12 (10^7 CFU/g) Prebiotic: 3 g inulin + 5g whey + 5 mg calcium + 500 IU vitamin D3 per serve	Hypocaloric diet (500 kcal/day reduction) + maintenance of pre-trial physical activity	A) 2 daily servings of fortified yogurt + hypocaloric diet (n=44) B) 2 daily servings low-fat yogurt + hypocaloric diet (n=45)	Reduced *FM in group A compared with group B.
Rabiei 2015^Citation43 Iran	Randomized, triple-blind, controlled study	12 weeks	40 adults with metabolic syndrome; Age: 59.0 ± 7.6 years; BMI: 32.4 ± 4.7 kg/m^2; 69.6% female; Attrition: 13%	Probiotic: 2 capsules daily containing 2×10^8 CFU Lactobacillus casei, Lactobacillus rhamnosus, Streptococcus thermophilus, Bifidobacterium breve, Lactobacillus acidophilus, Bifidobacterium longum, Lactobacillus bulgaricus Prebiotic: FOS	Diet based on ideal weight + maintenance of pre-trial physical activity	A) 2 synbiotic capsules daily + personalized diet plan (n=20) B) 2 placebo capsules daily + personalized diet plan (n=20)	Reduced ***BMI, ***WC, and ***HC in both groups but NS differences between groups.
Sanchez 2014^Citation69 Canada	Randomized, double-blind, placebo-controlled study	6 months: Phase 1: 12-weeks of weight loss Phase 2: 12-weeks of weight maintenance	105 healthy obese adults; Age: 36.0 ± 10 years; BMI: 36.0 ± 2.2 kg/m^2; 57% female; Attrition: not given	Probiotic: Lactobacillus rhamnosus CGMCC1.3724 (1.62 x 10^8 CFU) Prebiotic: Oligofructose and inulin	Phase 1: Personalized diet plan with a 500 kcal/day reduction Phase 2: Personalized diet plan without energy reduction	A) 2 synbiotic capsules daily + personalized diet plan (n=62) B) 2 placebo capsules daily + personalized diet plan (n=63)	Reduced *BW and *FM in group A females compared with group B females in both stages (NS difference when considering males and females together). NS differences in BW and FM in men in either group at either stage.
Sergeev 2020 ^Citation70 USA	Randomized, placebo-controlled study	12 weeks	20 overweight or obese adults; Age: 47.4 ± 12.3 years; BMI: 33.5 ± 5 kg/m^2; 75% female; Attrition: 0%	Probiotic: Probiotic capsules containing 15×10^9 CFU (Lactobacillus acidophilus DDS-1, Bifidobacterium lactis UAB1a-12, Bifidobacterium longum UAB1-14, and Bifidobacterium bifidum UABb-10) Prebiotic: Trans-galactooligosaccharide	Energy restricted diet recommended (low-carbohydrate, high-protein) – did not track adherence	A) Synbiotic + hypocaloric diet recommendations (n = 10) B) Placebo + hypocaloric diet recommendations (n = 10)	NS difference in BW, BMI, FM, and BFP within or between groups.

Notes: Significance is denoted by *p<0.05, **p<0.01, or ***p<0.001. Sample size refers to the number of participants included in the final analysis.

Abbreviations: BC, buttock circumference; BF, body fat; BFM, body fat mass; BFP, body fat percentage; BMI, body mass index; BW, body weight; FFM, fat-free mass; FM, fat mass; HC, hip circumference; NS, non-significant; TC, thigh circumference; TF, trunk fat; WC, waist circumference; WHR, weight-to-height ratio.

Figure 2 Forest plots of the effects of probiotics. Forest plots of the effects of probiotics on (A) body weight; (B) BMI; (C) fat mass; and (D) waist circumference. Analyses consider the pooled mean difference (MD) between baseline and end-of-treatment in patients receiving microbiome-targeted therapies as an adjunct to exercise/diet compared with patients receiving exercise/diet only. MDs are presented with the 95% CI for each study and for the combined results.

Figure 3 Forest plots of the effects of synbiotics. Forest plots of the effects of synbiotics on (A) body weight (kg); (B) BMI (kg/m²); (C) fat mass (kg); and (D) waist circumference (cm). Analyses consider the pooled mean difference (MD) between baseline and end-of-treatment in patients receiving microbiome-targeted therapies as an adjunct to exercise/diet compared with patients receiving exercise/diet only. MDs are presented with the 95% CI for each study and for the combined results.

Figure 4 Risk of bias assessment using the RoB-2 tool. The risk was assessed using the Cochrane Collaboration’s tool for qualitatively assessing the risk of bias.³² (A) Details of all included studies; (B) overall summary.

Figure 5 Funnel plot. Funnel plot for the meta-analysis of body weight in the probiotic group. The standard error and effect size are shown on the y- and x-axis, respectively. The circles represent the individual studies in the analysis.

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