Gut Microbiota, Prebiotics, Probiotics, and Synbiotics in Management of Obesity and Prediabetes

Review of Randomized Controlled Trials

Elena Barengolts, MD


Endocr Pract. 2016;22(10):1224-1234. 

In This Article

Abstract and Introduction


Objective: To review the data from randomized controlled trials (RCTs) for the roles of microbiota, pre-, pro- and synbiotics in metabolic conditions (obesity, prediabetes, and diabetes mellitus type 2 [DM2]).

Methods: Primary literature was reviewed on the topics including RCTs of pre-, pro- and synbiotics use for metabolic disease.

Results: Gut bacteria (microbiota) benefit digestion and have multiple other functions. Microbiota could increase harvesting of energy from the food and cause subclinical inflammation seen in metabolic disorders. Diet-related interventions including prebiotics, probiotics, and synbiotics (combining pre-and probiotics) may benefit metabolic conditions. Prebiotics are complex carbohydrates (i.e., dietary fiber). Results of RCTs of prebiotics suggested a neutral effect on body weight, decreased fasting and postprandial glucose, and improved insulin sensitivity and lipid profile. Some inflammation markers were reduced, sometimes substantially (20–30%). RCTs for probiotics demonstrated significant but small effects on body weight (<3%) and metabolic parameters. The effect was seen mostly with fermented milk or yogurt compared to capsule form, consumption for at least 8 weeks, and use of multiple rather than a single bacterial strain. Changes in microbiota were seen at times with both pre- and probiotics. Pickled and fermented foods, particularly vegetables and beans, could serve as a dietary source of pre-, pro-, and synbiotics. These foods showed possible benefits for morbidity and mortality in prospective cohort studies.

Conclusion: Pre-, pro-, and synbiotics could prove useful, but further research is needed to clarify their clinical relevance for the prevention and management of metabolic disease.


Nutrition affects health and disease. Homo sapiens evolved ~100,000 years ago in an environment with sporadic food availability favoring evolutionary selection of "thrifty" genes promoting preservation and storage of nutrients.[1] Leap to the present, and nutrient abundance instigates human obesity of epidemic proportion. The consequences of obesity, diabetes mellitus type 2 (DM2), nonalcoholic fatty liver disease (NAFLD) or nonalcoholic steatohepatitis (NASH), cardiovascular disease (CVD), and cancer, are main causes of morbidity and mortality in developed countries.[2,3] Humans have coevolved with microbacteria, the first form of life to appear on Earth ~3.5 billion years ago.[4] Bacteria in the gut are called gut microbiota (called GMB or microbiota for the purpose of this review). "Microbiota" comes from the Greek "mikros" meaning small and "bios" meaning life. Emerging evidence suggest an essential role of microbiota in human health and disease including digestion, energy, and glucose metabolism, as well as immunomodulation and brain function.[4–9] Dietrelated interventions causing beneficial changes of GMB could also include pre-, pro-, and synbiotics (combining prebiotics and probiotics). There are many challenges in studying the usefulness of pre-, pro-, and synbiotics for human health. Multiple hypotheses still need to be tested and controversies resolved. For example, it is not clear whether potential health benefits result from the interaction of "-biotics" with the microbiota and if the effect sizes seen in studies are clinically relevant. This review focuses on published randomized controlled trials (RCTs) of microbiota and pre-, pro-, and synbiotics for metabolic conditions including obesity, prediabetes, and DM2.