Table 2.

Summary of studies investigating the effects of probiotics, prebiotics, and synbiotics on obesity and depression

Intervention	Outcomes	Key findings	Study (Author, Year)
Various probiotics strains and combinations	Mental healt, gut health, systemic effects	Probiotics showed promise across multiple domains including mental health; emphasized standardization and personalization	Chao et al,. 2025
Probiotics, prebiotics, synbiotics	Depression and anxiety scores	Probiotics significantly reduced depression, and anxiety; prebiotics had nonsignificant effect	Asad et al., 2025
Bifidobacterium longum 1714	Stress, memory, cortisol levels	Reduce stress and improved memory performance; lowered cortisol response	Patterson et al., 2024
Prebiotics, probiotics, synbiotics	Depression scores	Significant improvement in depressive symptoms with probiotics; prebiotics and synbiotics showed mixed results; stronger effects observed in studies with lower female participation and mild/ moderate depression	Zhang et al., 2023
Probiotic mix (Lactobacillus Bifidobacterium)	Body weight, depression/ anxiety scores, cognitive function	Improved neurobehavioral in symptoms and weight reduction; enhanced gut-brain axis function	Cai et al., 2023
Lactobacillus plantarum 299v	Depression scores (HAM-D), inflammatory markers	Significant reduction in depressive symptoms and IL-6 levels	Rudzki et al., 2019
Probiotic capsule (Lactobacillus acidophilus, Bifidobacterium bifidum)	Depression scores (BDI), BMI	Decrease depression scores and BMI; improved metabolic parameters	Kazemi et al., 2019
Probiotic mix (Lactobacillus acidophilus, Bifidobacterium bifidum, Lactobacillus casei)	Depression scores (DBI)	Significant reduction in depressive symptoms compared to placebo	Akksheh et al., 2016