THE ROLE OF GUT MICROBIOTA IN THE DEVELOPMENT OF OBESITY, TYPE 2 DIABETES, AND DEPRESSION - A REVIEW OF CURRENT LITERATURE 2020–2026
DOI:
https://doi.org/10.31435/ijitss.2(50).2026.5956Keywords:
Gut Microbiota, Dysbiosis, Obesity, Type 2 Diabetes, Depression, Gut–Brain Axis, Short-Chain Fatty Acids, Diet, Probiotics, PsychobioticsAbstract
Background: The gut microbiota constitutes a complex and functionally active ecosystem that is increasingly recognized as a potential contributor to metabolic, immunological, and neuroendocrine homeostasis. Between 2020 and 2026, research has shifted from taxonomic descriptions toward functional and multi-omic approaches, improving understanding of the potential involvement of the microbiome in chronic metabolic and psychiatric disorders. This review summarizes current evidence on gut dysbiosis in obesity, type 2 diabetes, and depression, and evaluates proposed microbiota-targeted interventions.
Methods:A narrative synthesis was conducted based on a targeted search of PubMed and PubMed Central for studies published between January 2020 and May 2026. After screening more than 100 records, 68 full-text articles were assessed, and 31 publications, including systematic reviews, meta-analyses, and selected primary studies, were included..
Results: Gut dysbiosis, characterized by reduced microbial diversity, depletion of butyrate-producing bacteria, alterations in intestinal barrier function, and metabolic endotoxemia, has been consistently reported in association with obesity, type 2 diabetes, and depression. In obesity and type 2 diabetes, dysbiosis has been linked to chronic low-grade inflammation, altered short-chain fatty acid signaling, and insulin resistance. In depression, proposed mechanisms include gut–brain axis dysregulation, alterations in tryptophan metabolism toward the kynurenine pathway, and neuroinflammatory processes; however, the strength of evidence remains less consistent compared with metabolic disorders. Dietary patterns, particularly Mediterranean- and high-fiber–based diets, appear to be the most consistently supported modifiable factors associated with beneficial microbiota profiles and metabolic outcomes. Microbiota-targeted interventions, including probiotics, prebiotics, synbiotics, and fecal microbiota transplantation, show biological plausibility and early clinical signals, but current evidence remains heterogeneous and not yet definitive.
Conclusions: Current evidence suggests that the gut microbiota may represent one component of a broader immunometabolic and neuroendocrine network potentially involved in the development of obesity, type 2 diabetes, and depression, rather than a primary causal driver. Routine clinical use of microbiota profiling is not currently supported. Nevertheless, microbiota-modulating strategies, particularly dietary interventions, may serve as adjunctive approaches alongside standard care. Further well-designed, standardized, and adequately powered prospective and interventional studies integrating metagenomic and functional data are needed to clarify clinical utility and causality.
References
Alqahtani, M. S. (2025). The gut microbiota–metabolic axis: Emerging insights from human and experimental studies on type 2 diabetes mellitus—a narrative review. Medicina (Lithuania), 61(11), 2017. https://doi.org/10.3390/MEDICINA61112017/S1
Anachad, O., Taouil, A., Taha, W., Bennis, F., & Chegdani, F. (2023). The implication of short-chain fatty acids in obesity and diabetes. Microbiology Insights, 16. https://doi.org/10.1177/11786361231162720
Arellano-García, L., Portillo, M. P., Hadjihambi, A., Martínez, J. A., & Milton-Laskibar, I. (2026). The gut–brain axis in obesity: Mechanisms, development, and therapeutic perspectives. Current Nutrition Reports, 15(1), 16. https://doi.org/10.1007/S13668-026-00732-W
Beswick, G., Major, N., Hendrickson, C., Kumar, V., Waller, M., Durrani, Z., Hotchkiss, S., Bala, A., & Taylor, V. H. (2025). A scoping review on the role of the microbiome as a factor in the bidirectional association between obesity and depression. Current Diabetes Reports, 25(1). https://doi.org/10.1007/S11892-025-01607-0
Borrego-Ruiz, A., & Borrego, J. J. (2025). The gut microbiome in human obesity: A comprehensive review. Biomedicines, 13(9), 2173. https://doi.org/10.3390/BIOMEDICINES13092173
Cao, J., Ma, J., Zha, X., Bian, X., Wang, W., & Liu, X. (2026). Gut microbiota dysbiosis in depression: Pathological correlations, molecular pathways, and therapeutic interventions. International Journal of Molecular Sciences, 27(3), 1530. https://doi.org/10.3390/IJMS27031530
Chen, X., Wang, Y., Lv, Y., Wang, H., Yang, Y., Tang, J., Shen, H., & Dai, Z. (2026). Gut microbiota signatures across BMI categories in adults and combined diagnostic value with clinical indicators for early obesity risk stratification. Frontiers in Microbiology, 16, 1734612. https://doi.org/10.3389/FMICB.2025.1734612
Chen, Y., Zhou, J., & Wang, L. (2021). Role and mechanism of gut microbiota in human disease. Frontiers in Cellular and Infection Microbiology, 11. https://doi.org/10.3389/FCIMB.2021.625913
Cheng, Z., Zhang, L., Yang, L., & Chu, H. (2022). The critical role of gut microbiota in obesity. Frontiers in Endocrinology, 13. https://doi.org/10.3389/FENDO.2022.1025706
Chong, S., Lin, M., Chong, D., Jensen, S., & Lau, N. S. (2025). A systematic review on gut microbiota in type 2 diabetes mellitus. Frontiers in Endocrinology, 15. https://doi.org/10.3389/FENDO.2024.1486793
Clerici, L., Bottari, D., & Bottari, B. (2025). Gut microbiome, diet and depression: Literature review of microbiological, nutritional and neuroscientific aspects. Current Nutrition Reports, 14(1), 30. https://doi.org/10.1007/S13668-025-00619-2
Crudele, L., Gadaleta, R. M., Cariello, M., & Moschetta, A. (2023). Gut microbiota in the pathogenesis and therapeutic approaches of diabetes. EBioMedicine, 97. https://doi.org/10.1016/J.EBIOM.2023.104821
Cryan, J. F., O’Riordan, K. J., Sandhu, K., Peterson, V., & Dinan, T. G. (2020). The gut microbiome in neurological disorders. The Lancet. Neurology, 19(2), 179–194. https://doi.org/10.1016/S1474-4422(19)30356-4
Doroszkiewicz, J., Groblewska, M., & Mroczko, B. (2021). The role of gut microbiota and gut-brain interplay in selected diseases of the central nervous system. International Journal of Molecular Sciences, 22(18). https://doi.org/10.3390/IJMS221810028
Fan, Y., & Pedersen, O. (2021). Gut microbiota in human metabolic health and disease. Nature Reviews. Microbiology, 19(1), 55–71. https://doi.org/10.1038/S41579-020-0433-9
Fu, J., Zheng, Y., Gao, Y., & Xu, W. (2022). Dietary fiber intake and gut microbiota in human health. Microorganisms, 10(12), 2507. https://doi.org/10.3390/MICROORGANISMS10122507
Gómez-García, I., Besné-Eseverri, I., Portillo, M. P., Fernández-Quintela, A., Díaz, L. E., Riezu-Boj, J. I., Milagro, F. I., & Trepiana, J. (2025). Oral administration of an Opuntia ficus-indica fruit extract induces changes in gut microbiota composition: Relationship with its anti-obesity and anti-steatotic effects in rats fed a high-fat high-fructose diet. Foods, 14(16), 2891. https://doi.org/10.3390/FOODS14162891
Góralczyk-Bińkowska, A., Szmajda-Krygier, D., & Kozłowska, E. (2022). The microbiota-gut-brain axis in psychiatric disorders. International Journal of Molecular Sciences, 23(19). https://doi.org/10.3390/IJMS231911245
Halabitska, I., Petakh, P., Kamyshna, I., Oksenych, V., Kainov, D. E., & Kamyshnyi, O. (2024). The interplay of gut microbiota, obesity, and depression: Insights and interventions. cellular and molecular life sciences: CMLS, 81(1). https://doi.org/10.1007/S00018-024-05476-W
He, Y., Liu, L., Liu, Y., Jia, J., Chen, Y., Zhang, X., & Liu, Y. (2026). Exploring the gut microbiome in type 2 diabetes across different insulin resistance levels: A machine learning approach. Frontiers in Nutrition, 13, 1747767. https://doi.org/10.3389/FNUT.2026.1747767/FULL
Islam, M. M., Islam, M. M., Rahman, M. A., Ripon, M. A. R., & Hossain, M. S. (2023). Gut microbiota in obesity and related complications: Unveiling the complex interplay. Life Sciences, 334. https://doi.org/10.1016/J.LFS.2023.122211
Jiang, R., Zheng, L., Fang, J., Guan, Q., Yuan, H., Liang, J., Zhang, J., Han, Q., & Liu, M. (2026). Targeting the gut microbiome for type 2 diabetes management: A scoping review of systematic reviews and meta-analyses. Frontiers in Endocrinology, 17. https://doi.org/10.3389/FENDO.2026.1682174
Jin, X., Chen, X., Chen, H., & Hong, X. (2026). Gut microbiota and type 2 diabetes: Genetic associations, biological mechanisms, drug repurposing, and diagnostic modeling. International Journal of Molecular Sciences, 27(2), 1070. https://doi.org/10.3390/IJMS27021070/S1
Kumar, M., Singh, S., Ojha, R., Kriti, M., Park, G., Verma, V., Pal, N., Sharma, P., Shubham, S., Pandey, M. K., Parasannanavar, D. J., Sarma, D. K., Tiwari, R. R., & Nagpal, R. (2026). Gut microbiome disparities reflect type 2 diabetes progression and medication status. IScience, 29(3), 115156. https://doi.org/10.1016/J.ISCI.2026.115156
Lei, P., Qi, Z., Ma, Q., Zhao, B., Wen, B., Jiang, W., Xi, W., Liu, Y., Xun, Y., Zhang, S., Wang, Y., Guo, Y., Wang, W., Ma, X., Jia, M., & Fan, Y. (2026). Gut microbiota reshapes host energy metabolism to modulate depressive behaviors. Gut Microbes, 18(1), 2662556. https://doi.org/10.1080/19490976.2026.2662556
Liu, B. N., Liu, X. T., Liang, Z. H., & Wang, J. H. (2021). Gut microbiota in obesity. World Journal of Gastroenterology, 27(25), 3837. https://doi.org/10.3748/WJG.V27.I25.3837
Luo, L., Xue, M., Sun, L., & Dai, Z. (2026). Gut microbiota in obesity management: From microbial clocks to precision microbial therapies. Frontiers in Cellular and Infection Microbiology, 16, 1705021. https://doi.org/10.3389/FCIMB.2026.1705021
Masi, D., Watanabe, M., & Clément, K. (2026). Gut microbiome and obesity care: Bridging dietary, surgical, and pharmacological interventions. Cell Reports Medicine, 7(2), 102573. https://doi.org/10.1016/J.XCRM.2025.102573
Moon, H. J., Cha, Y. S., & Kim, K. A. (2026). Whole blackcurrant (Ribes nigrum) alleviates high‐fat diet induced‐obesity and colonic inflammation by modulating the gut microbiota in mice. Molecular Nutrition & Food Research, 70(7), e70462. https://doi.org/10.1002/MNFR.70462
Qureshi, U., Bajwa, A., Aslam, Z., Aggrey, A., Nawaz, U. H., & Ul Ain, Q. (2025). Gut microbiota modulation in type 2 diabetes and cardiometabolic risk: A systematic review. Cureus, 17(9). https://doi.org/10.7759/CUREUS.92020
Raczkowska, A., Arak, K., & Jaworska, K. (2024). [the role of gut microbiota and its metabolites in obesity and diabetes]. Postepy Biochemii, 70(4), 508–521. https://doi.org/10.18388/PB.2021_569
Rondinella, D., Raoul, P. C., Valeriani, E., Venturini, I., Cintoni, M., Severino, A., Galli, F. S., Mora, V., Mele, M. C., Cammarota, G., Gasbarrini, A., Rinninella, E., & Ianiro, G. (2025). The detrimental impact of ultra-processed foods on the human gut microbiome and gut barrier. Nutrients, 17(5), 859. https://doi.org/10.3390/NU17050859
Ross, F. C., Patangia, D., Grimaud, G., Lavelle, A., Dempsey, E. M., Ross, R. P., & Stanton, C. (2024). The interplay between diet and the gut microbiome: Implications for health and disease. Nature Reviews. Microbiology, 22(11), 671–686. https://doi.org/10.1038/S41579-024-01068-4
Ruan, Z., Liu, J., & Zhao, J. (2025). Causal associations between gut microbiota and type 2 diabetes mellitus subtypes: A mendelian randomization analysis. BMC Endocrine Disorders, 25(1), 79. https://doi.org/10.1186/S12902-025-01863-X
Sá Filho, A. S., Souza, T. B., Martins, J. L. R., Dietz, G. P. H., Fernandes, K. F., Sá, S. de, Inacio, P. A., Oliveira-Silva, I., Pedrino, G., Aprigliano, V., Chiappa, G. R., & Fajemiroye, J. O. (2026). “attacking” the gut–brain axis with psychobiotics: An umbrella review of depressive and anxiety symptoms. Pharmaceuticals, 19(1), 156. https://doi.org/10.3390/PH19010156/S1
Sasidharan Pillai, S., Gagnon, C. A., Foster, C., & Ashraf, A. P. (2024). Exploring the gut microbiota: Key insights into its role in obesity, metabolic syndrome, and type 2 diabetes. The Journal of Clinical Endocrinology and Metabolism, 109(11), 2709–2719. https://doi.org/10.1210/CLINEM/DGAE499
Senesi, P., Ferrulli, A., Luzi, L., & Terruzzi, I. (2021). Diabetes mellitus and cardiovascular diseases: Nutraceutical interventions related to caloric restriction. International Journal of Molecular Sciences, 22(15), 7772. https://doi.org/10.3390/IJMS22157772
Su, Y., & Xia, Y. (2026). Gut microbiota dysbiosis and depression: Bidirectional interactions, mediating pathways, and microecological therapeutics. Current Research in Food Science, 12, 101372. https://doi.org/10.1016/J.CRFS.2026.101372
Tavassol, Z. H., Ejtahed, H. S., Khalagi, K., Marvasti, F. E., Mahmoudian, E., Rafiei, N., Sajadi, N. A., Nabipour, I., Siadat, S. D., Ostovar, A., Hasani-Ranjbar, S., & Larijani, B. (2026). Exploring the gut microbiota alterations with obesity in older adults: a case-control study in the context of Bushehr Elderly Health (BEH) program. Journal of Health, Population, and Nutrition, 45(1), 84. https://doi.org/10.1186/S41043-025-01230-5
Ur Rehman, M., Saeed, H., Omer, O., & Tashfeen, S. (2025). Gut microbiota-directed interventions in type 2 diabetes: A systematic review of clinical outcomes and complication risk. Cureus, 17(10). https://doi.org/10.7759/CUREUS.95045
Yang, M., Wang, L., Zhou, P., & Xia, J. (2026). Causal effects of yogurt intake on gut microbiota: A European Mendelian randomization study. International Journal of Genomics, 2026(1), 2921181. https://doi.org/10.1155/IJOG/2921181
Zhang, K., Zhang, Q., Qiu, H., Ma, Y., Hou, N., Zhang, J., Kan, C., Han, F., Sun, X., & Shi, J. (2024). The complex link between the gut microbiome and obesity-associated metabolic disorders: Mechanisms and therapeutic opportunities. Heliyon, 10(17), e37609. https://doi.org/10.1016/J.HELIYON.2024.E37609
Zheng, B., Shen, X., Han, N., Guo, X., & Wan, S. (2026). The microbiota-gut-brain-epigenome axis as a novel therapeutic target for decoding postpartum depression. Frontiers in Medicine, 13, 1778348. https://doi.org/10.3389/FMED.2026.1778348
Zhou, Q., Tang, C., Pan, X., Lu, Z., Chen, R., & Gong, X. (2026). Joint association of diet index for gut microbiota and MVPA with central obesity: The mediating role of biological age. Food Science & Nutrition, 14(2), e71516. https://doi.org/10.1002/FSN3.71516
Zhu, F., Tu, H., & Chen, T. (2022). The microbiota-gut-brain axis in depression: The potential pathophysiological mechanisms and microbiota combined antidepression effect. Nutrients, 14(10). https://doi.org/10.3390/NU14102081
Zhu, Z., Cheng, Y., Liu, X., Xu, X., Ding, W., Ling, Z., Liu, J., & Cai, G. (2025). The microbiota-gut-brain axis in depression: Unraveling the relationships and therapeutic opportunities. Frontiers in Immunology, 16. https://doi.org/10.3389/FIMMU.2025.1644160
Downloads
Published
Issue
Section
License
Copyright (c) 2026 Wiktoria Waldon, Filip Witowicz, Julia Glińska, Weronika Spychalska, Kornelia Kaźmierkiewicz-Makanga, Maksymilian Bogacz, Aleksandra Krawczyk, Paulina Sumlet, Maria Gofron, Michał Duliński
This work is licensed under a Creative Commons Attribution 4.0 International License.
All articles are published in open-access and licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0). Hence, authors retain copyright to the content of the articles.
CC BY 4.0 License allows content to be copied, adapted, displayed, distributed, re-published or otherwise re-used for any purpose including for adaptation and commercial use provided the content is attributed.
How to Cite
