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Can Probiotics Improve Weight, Blood Sugar & Metabolic Health?

Written by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

Probiotic supplements have produced intriguing benefits in people with diabetes, metabolic syndrome, liver disease, and obesity. Which biochemical markers have been improved? Learn more here.

Probiotics & Metabolism

Metabolic syndrome, diabetes, and obesity are among the most common and most debilitating diseases in modern humans. Probiotics are currently under investigation for their potential to prevent and alleviate the markers and root causes of these conditions, and early results have been promising.

If any of these conditions apply to you, talk to your doctor before supplementing with probiotics. Together, you can determine whether probiotics could be beneficial in your case and which strains are most likely to help.

Insufficient Evidence For

The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of probiotics for any of the below-listed uses. Remember to speak with a doctor before taking probiotic supplements, and never use it in place of something your doctor recommends or prescribes.

1) Weight Loss

According to a few studies, consuming probiotics may reduce body weight and BMI. A greater effect is achieved in overweight subjects, when multiple species of probiotics are consumed in combination or when they are taken for more than 8 weeks [1].

L. rhamnosus induced weight loss in women, reducing fat mass and circulating leptin concentrations [2].

L. gasseri significantly decreased body weight and visceral and subcutaneous fat in adults with a tendency toward obesity [3].

Despite there being no change in behavior or diet, the administration of L. gasseri modestly reduced weight and waist and hip circumference in obese and overweight adults [4].

L. gasseri significantly decreased BMI, abdominal visceral fat, waist and hip circumferences, and body fat mass in healthy Japanese adults. However, constant consumption of this probiotic may be required to maintain this effect [5].

Both L. rhamnosus and L. gasseri also significantly lowered weight in mice [6, 7, 8] while L. gasseri was also shown to reduce body weight in rats [9].

Some research has suggested a link between gut flora and body weight. In several clinical trials, certain Lactobacillus probiotics induced weight loss in adults.

2) Obesity

Intestinal microbiota can affect host adiposity and regulate fat storage [10].

Bifidobacteria content was higher in children of normal weight than those who were showing signs of becoming overweight [11]. Similarly, the presence of B. animalis was found to be negatively associated with BMI in humans [12, 13].

The intake of synbiotics (probiotics + prebiotics) in obese children resulted in a significant reduction in BMI, waist circumference, and some cardiometabolic risk factors, such as TC, LDL-C, and TAG [14].

L. acidophilus, B. animalis ssp. lactis and L. casei reduced BMI, fat percentage, and leptin levels in overweight individuals [14].

Daily ingestion of milk containing B. animalis ssp. lactis significantly reduced the BMI, total cholesterol, low-density lipoprotein, and inflammatory markers in humans [15].

A low-calorie diet supplemented with L. plantarum reduced BMI in Russian adults with obesity and hypertension [14].

L. gasseri prevented abdominal fat accumulation [16] and decreased body weight in adults with obese tendencies [3].

B. breve lowered fat mass and improved GGT and hs-CRP in adults with obese tendencies [17].

L. rhamnosus improved markers of liver health in obese children with liver dysfunction noncompliant with lifestyle interventions [18].

L. paracasei decreases caloric intake in both human and animal subjects [19].

Oral administration of B. longum, B. bifidum, B. infantis, and B. animalis decreased glucose levels, ameliorated insulin resistance and reduced the expressions of inflammatory adipocytokines in obese mice [20].

B. breve reduced body weight gain and accumulation of visceral fat in a dose-dependent manner, and improved serum levels of total cholesterol, fasting glucose, and insulin in a mouse model of diet-induced obesity [21].

C. butyricum reduced fat accumulation in liver and blood, lowered insulin levels and improved glucose tolerance and insulin sensitivity in obese mice. Furthermore, C. butyricum administration ameliorated GI and fat tissue inflammation [22].

Water extract of L. paracasei reduced body weight in obese rats. It decreased the formation of lipid plaques in the aorta, reduced fat cell size and inhibited fat absorption, thereby reducing fat production (lipogenesis) [23].

NOTE: Although some studies show beneficial effects of L. reuteri in obesity-related symptoms, in one study, this species was more abundant in obese people than in people of healthy weight [24].

Obesity is associated with dysregulated gut bacteria, and administering certain probiotics reduced body weight in clinical studies of obese people.

3) Blood Glucose & Insulin Sensitivity

Several studies suggest that probiotics may have a significant effect on lowering fasting blood glucose and insulin in diabetics [25, 26].

L. plantarum reduced glucose levels in postmenopausal women [14].

L. casei improved insulin sensitivity in subjects with metabolic syndrome [14].

Furthermore, long‐term ingestion of L. casei reduced insulin resistance and glucose intolerance in rats fed a high‐fat diet [27], rats with hyperinsulinemia [28], and obese mice [27].

L. plantarum significantly reduced blood glucose levels in response to insulin in mice on a high-fat diet [29].

An L. paracasei probiotic was shown to improve many aspects of insulin resistance, such as fasting response, hormonal homeostasis, and glycemic control in rats [30].

gasseri increased energy expenditure, reduced blood glucose, improved glucose tolerance, attenuated inflammation [31], and reduced insulin levels in rats [32].

In patients with metabolic syndrome and postmenopausal women, Lactobacillus probiotics reduced blood glucose and increased insulin sensitivity.

4) Diabetes

Many researchers believe that the gut microbiota play an important role in the pathogenesis and metabolic disturbances of type 2 diabetes mellitus (T2DM) [33].

Gut microbiota of adults with T2DM is quite different from the microbiota of nondiabetic adults. The content of Bifidobacteria is decreased, whereas Enterococci and Escherichia coli are increased significantly [33].

Probiotics may improve carbohydrate metabolism, total cholesterol, fasting blood glucose, insulin sensitivity, and antioxidant status and reduce metabolic stress in subjects with T2DM [33, 14].

Certain probiotics (L. lactis, Bifidobacteria) secrete an insulin analog [10], and they can modestly improve fasting insulin in people with T2DM [34].

In Humans:

In T2DM patients, L. acidophilus and B. animalis increased good cholesterol (HDL-C) levels and decrease the LDL-C/HDL-C ratio [14]. They further significantly decreased fasting blood glucose and exerted antioxidant effects [14].

A synbiotic containing L. acidophilus, L. casei, B. bifidum, and inulin decreased fasting plasma glucose, blood insulin concentrations and increased insulin sensitivity in overweight diabetic patients with coronary heart disease. In addition, HDL-cholesterol levels were increased [35].

Consumption of a synbiotic containing B. coagulans reduced insulin levels, improved blood lipid profile and increased good cholesterol (HDL-C) in type 2 diabetes (T2D) patients [14, 36, 37].

Similarly, consumption of a synbiotic with B. coagulans improved NO, MDA [38], hs-CRP, uric acid, and plasma total GSH levels in diabetic patients [39].

L. acidophilus preserved insulin sensitivity in men with T2DM [14].

Soy milk containing L. plantarum has antioxidative properties and decreases DNA damage in patients with T2DM [14].

Diabetic patients who develop foot ulcers are at more risk of dying prematurely than those without the complication. B. subtilis shows antimicrobial activity against four diabetic foot ulcer bacterial pathogens [40].

Perhaps unsurprisingly, given their more general effect on blood glucose and insulin sensitivity, probiotics have had diverse positive effects on people with diabetes. These have included reducing the incidence of foot ulcers, improving blood lipid profiles, and preserving insulin sensitivity.

Animal studies:

B. animalis ssp. lactis reduces weight gain and fat mass, improves glucose tolerance [41], decreases fasting insulin and blood glucose, and significantly improves insulin tolerance in mice with diabetes [42].

B. bifidum decreased fasting blood glucose and insulin in diabetic rats [43].

B. bifidum stabilized blood sugar, lower cholesterol levels in serum, and improve metabolic activity in mice [44].

L. brevis decreased glucose levels in diabetic rats [45].

L. gasseri decreased blood glucose and improved glucose sensitivity in diabetic mice [46].

johnsonii inhibits hyperglycemia, reduced the elevation of blood glucose and glucagon levels in diabetic rats [47], and inhibited insulin resistance in mice [48].

Administration of L. casei and B. bifidum alone and in combination ameliorated hyperglycemia, dyslipidemia, and oxidative stress in diabetic rats [43].

L. casei significantly improved glucose intolerance, dyslipidemia, immune-regulatory properties, and oxidative stress in mice with T2D [49].

Treating diabetic mice with nonviable L. salivarius reversed gut microbial imbalance, restored mucosal antibacterial protein and lessened endotoxin levels [50].

L. rhamnosus exerted an anti-diabetic effect in mice, with an anti-hyperglycemic effect in several rodent models. L. rhamnosus further improves glucose tolerance and enhances insulin sensitivity [51].

Treatment with L. plantarum improved blood glucose, hormones, and lipid metabolism in diabetic rats [52].

5) Metabolic Syndrome

B. animalis ssp. lactis significantly reduced BMI, total cholesterol, low-density lipoprotein and inflammatory cytokines in patients with metabolic syndrome [53].

L. plantarum reduced total cholesterol, LDL-cholesterol, glucose and homocysteine levels in postmenopausal women with metabolic syndrome [54].

L. casei improved insulin sensitivity in subjects with metabolic syndrome [14].

L. gasseri decreased food and energy intake, and improved body weight, insulin resistance and cholesterol levels in rats with metabolic syndrome (MS) [55].

As in diabetes, probiotics appear to have several benefits for metabolic syndrome: in various studies, they have reduced cholesterol, glucose, inflammation, and homocysteine.

6) Liver Disease

Probiotics found in yogurt, L. delbrueckii ssp. bulgaris and S. thermophilus improved liver function [14].


Some probiotics and synbiotics improved liver and metabolic parameters in patients with non-alcoholic fatty liver disease (NAFLD) [14].

In patients with NAFLD, L. acidophilus and B. lactis reduced serum levels of ALT, ASP, TC, and LDL-C [14].

In obese children with NAFLD, L. rhamnosus restored liver function [14].

Bifidobacteria, Lactobacilli, and S. thermophilus treatment for 4 months improved fatty liver severity and decreased BMI of children with NAFLD [14].

L. rhamnosus protected against NAFLD in mice, possibly by increasing beneficial bacteria in the distal small intestine and attenuating liver fat accumulation and portal alanine-aminotransferase concentrations [56].

Treatment with L. plantarum for 5-weeks restored liver function in rats with non-alcoholic fatty liver disease (NAFLD) and decreased the levels of fat accumulation in the liver. In addition, the bacterium significantly reduced proinflammatory cytokines [57].

L. casei protected against the onset of NAFLD in mice [58], and suppressed nonalcoholic steatohepatitis development. According to some researchers, this probiotic may reduce blood lipopolysaccharide concentrations, suppress inflammation and fibrosis in the liver and reduce colon inflammation [59].

A L. paracasei synbiotic (containing arabinogalactan, fructooligosaccharides) lessened NAFLD progression in rats, lowered inflammatory markers and reduced the severity of liver injury and insulin resistance [30].

L. johnsonii protected mice with NAFLD from liver steatosis and liver cell death [48].

C. butyricum increased cholesterol degrading enzymes and improved NAFLD in rats on a high-fat diet [60].

In patients with NAFLD, probiotics improved markers of metabolic health and BMI.


A synbiotic that contains five probiotics (L. plantarum, L. delbrueckii, L. acidophilus, L. rhamnosus, B. bifidum, and inulin) over 6 months in adults with nonalcoholic steatohepatitis (NASH) produced a significant decrease in intrahepatic triglyceride (IHTG) levels [14].

B. longum and fructo-oligosaccharides (FOS) significantly reduced AST, CRP, HOMA-IR, blood endotoxin and steatosis in patients with NASH [61].

L. paracasei lowered liver fat deposition and serum ALT level in mice with NASH [62].

Probiotic and synbiotic supplements also improved markers of liver health in people with NASH.

Alcohol-Induced Liver Injury

In mice, L. rhamnosus protected against alcoholic liver injury [63, 64].

L. casei attenuated alcohol-induced liver cell damage [65].

In chronic alcohol-induced mice, whey fermented with L. casei significantly attenuated the increased levels of ALT, AST and triglyceride levels, increased antioxidant activity, and improved liver parameters [66].

L. paracasei reduced total blood and liver cholesterol in rats and decreased liver damage due to alcohol intake [67].

L. fermentum significantly alleviated liver damage in mice with alcoholic liver disease [68, 69].

Oral administration of L. brevis ameliorated alcohol-induced liver injury and the fatty liver in mice. It significantly inhibited ALT and AST increase and decreased TG and total cholesterol in the liver [70].


Treatment of obstructive jaundice in rats with L. plantarum returned active liver barrier functions [71].

Liver Injury

L. plantarum protects against oxidative stress and liver inflammatory injury in mice [72].

L. casei significantly improved the survival of rats with liver injury, via its anti-oxidative and anti-inflammatory capacities [73].

Pretreatment with L. salivarius improved acute liver injury in rats [74].

L. salivarius is believed to promote health in acute liver failure [75].

L. paracasei restored gut microbiota and attenuated ischemia/reperfusion-related liver injury in rats [76].

S. boulardii effectively prevented liver injury induced by Salmonella Enteritidis infection in mice [77].


B. faecium and B. subtilis shifted the intestinal microbiota of patients with liver cirrhosis back towards levels observed in healthy subjects. These probiotics also reduced circulating endotoxin levels in cirrhotic patients with endotoxemia [78].

B. longum and FOS improved biochemical parameters and neuropsychological tests in cirrhotic patients with minimal hepatic encephalopathy (MHE) [79].

S. boulardii promoted liver function and slowed down the progress of liver fibrosis in rats [80].

In patients with cirrhosis, Bifidobacterium probiotics restored normal gut flora and improved biochemical and neuropsychological markers associated with liver damage.


Probiotic supplements have produced a number of remarkable benefits to metabolic health. In various clinical studies, probiotics have lowered blood glucose, maintained insulin sensitivity, reduced BMI, promoted fat loss, and decreased markers of liver damage. These results lend support to the models of obesity and metabolic syndrome that depend on dysregulation of the gut flora.

Further Reading

We’ve compiled deep dives into each potential benefit of probiotics. Check them out here:

About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.


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