Probiotics & Fiber Stopped Drug-Induced Weight Gain In Schizophrenic Patients

A recent peer-reviewed study published on May 15th Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center showed promising results from two randomized clinical trials registered at, Identifier NCT03379597.

The studies showed promise for attenuating weight gain in patients taking the second-generation antipsychotic drug Olanzapine. Two groups of participants in this study took either Probiotics or Fiber along with Olanzapine for a total of 12-weeks or Probiotics and FIber with Olanzapine for the same amount of time. The results were fascinating. 

Antipsychotic Drugs Often Cause Weight Gain


The study stated that antipsychotics caused weight gain and insulin resistance is a common side effect of taking certain Antipsychotic drugs. It was hypothesized that one reason for this was because of alterations to the gut flora in the microbiome. It was confirmed previously that out of all SGA's Olanzapine elicits the most weight. Shockingly, 80% of patients taking Olanzapine gained more than 7% of their starting body weight.

Two Groups

In this study, two randomized clinical trials were carried out on a total of 110 men and women from China. The first group contained 90 patients that took either Olanzapine with probiotics or Olanzapine with monotherapy. The second group took Olanzapine with probiotics and fiber or Olanzapine with monotherapy. Both groups took followed this routine for a total of 12-weeks.

Two sequential, randomized clinical trials were conducted. In Study 1, 90 drug-naïve, first-episode schizophrenia patients were randomized to receive either olanzapine plus probiotics or olanzapine monotherapy for 12 weeks. In Study 2, 60 drug-naïve, first-episode schizophrenia patients were randomly assigned to receive either olanzapine plus probiotics and dietary fiber or olanzapine monotherapy for 12 weeks.

Probiotic Strains, Fiber And Dosage


The probiotic strains used in the trials were a mix of Bifidobacterium, Lactobacillus, and Enterococcus but specific strains were not mentioned. The CFU count was at concentrations ≥5.0 × 107 cfu/g. The fiber used was 10mg of Momordica charantia with the Prebiotic fructooligosaccharides and the second fiber used was a 20mg mix of kudzu starch, inulin, and resistant dextrin. The participants were asked to take both the fiber and probiotics twice daily.


Medical history, physical examination, demographics, height, weight, and PANSS Scores (Psychopathologic symptoms) were all recorded beforehand. So were fasting glucose, lipids, insulin, liver function, blood tests, and an ECG test was also performed. Throughout this trial, these baseline tests were repeated a further three times.

Conclusion: Study Results

To confirm the results of this trial the body weight in kg was divided by the height squared. Insulin, fasting glucose, lipid metabolism changes, HDL-C, LDL-C, and total cholesterol were also measured. This data set made it easy to see if probiotics along with fiber were able to have a weight loss effect or not.

Group 1 Results


Olanzapine With Bifidobacterium Lactobacillus Probiotics.

Olanzapine Alone.

Weight In KG






Fasting Insulin, µIU/mL 



Cholesterol, mmol/L 



Group 2 Results


Olanzapine With Bifidobacterium Lactobacillus Probiotics WITH Fiber.

Olanzapine Alone.

Weight In KG






Fasting Insulin, µIU/mL 




Cholesterol, mmol/L 



The results clearly showed that taking probiotics alone with Olanzapine did not affect the total KG body weight of participants in group 1. Luckily, the second study did confirm that adding fiber with the probiotic supplement did have an effect on total KG. Fasting insulin was also increased in the second group but the effects on cholesterol were insignificant. It's thought that results were possible because of how the dietary fiber was able to selectively grow some bacteria. Furthermore, studies like this one have shown that the gut flora in obese individuals from those with a healthy weight.

Reference: Jing Huang, Dongyu Kang, Fengyu Zhang, Ye Yang, Chenchen Liu, Jingmei Xiao, Yujun Long, Bing Lang, Xingjie Peng, Weiyan Wang, Xiaoyi Wang, Fangkun Liu, John M Davis, Jingping Zhao, Renrong Wu, Probiotics Plus Dietary Fiber Supplements Attenuate Olanzapine-Induced Weight Gain in Drug-Naïve First-Episode Schizophrenia Patients: Two Randomized Clinical Trials, Schizophrenia Bulletin, 2022;, sbac044,

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