We once thought that weight loss was all about calories in, calories out, or just diet and exercise. Or perhaps, it’s in your genes or hormones like leptin. However, your gut bacteria might actually have more to do with your weight than you think. Read this post to learn about how probiotics could help you lose weight and improve your metabolism.
Why Do Probiotics help with Weight Loss?
1) Gut Bacteria of Obese People Can Harvest More Calories from Foods
In mice and rats, obesity-related microbes can harvest more energy from foods than the microbes that are found in lean animals .
Compared with lean mice with normal genes (wild-type), the gut bacteria of obese mice have more genes that can burn carbohydrates for energy .
2) Bacterial Metabolism and Metabolites Can Change Your Metabolism
Intestinal microbiota can affect host adiposity and regulate fat storage .
In mice, diet accounts for 57% of changes in their gut microbiome .
3) Fecal Transplants Bring Along the Donor’s Metabolism
Gut bacteria from stools of healthy and lean humans transferred to obese people with type 2 diabetes increased insulin sensitivity and gut bacteria diversity . However, this study did not observe significant changes in body mass index 6 weeks after the transfer.
In a case study, fecal matter was transplanted from an overweight donor to a lean patient for C. difficile infection treatment. After the transplant, the recipient had increased appetite and rapid unintentional weight gain that could not be explained by the recovery from the C. difficile infection alone .
In rats that are obese and insulin resistant, feeding them with antibiotics or transplanting them with fecal matters from healthy rats reversed obesity and insulin resistance .
In identical twin rats that have discordant phenotypes (e.g., one obese and one lean, despite identical genetics), it also appears that the gut bacteria control their metabolism. Germ-free mice (with no gut bacteria) populated with the obese twin had increased fat cells and reduced gut bacteria diversity compared to mice that were populated with the lean twin’s fecal matter .
In humans, more clinical studies would be necessary to determine whether fecal microbiota transplants can have long-term effects on insulin sensitivity or weight, even though fecal microbiota transplant can improve the gut microbiome for up to 24 weeks .
Presently, there are several phases 2 and 3 clinical trials for fecal microbiota transplant .
While results thus far have shown that fecal microbiota transplant is a promising therapy for metabolic problems, it does come with risks, including :
- Risks of infections getting carried over with the stool transplant
- Known side effects include diarrhea or fever
- Potential other negative traits or health problems could also be transferred along with the gut bacteria
4) Gut Bacteria Can Control Appetite and Satiety
5) Reduces Inflammation from Leaky Gut
Weight gain is associated with leaky gut (intestinal permeability) because high-fat diets can lead to leaky gut and thus circulating lipopolysaccharides in the bloodstream . This is called metabolic endotoxemia.
In a clinical trial with probiotic as an intervention for metabolic syndrome, the probiotic treatment led to a significant reduction in tissue inflammation and leaky gut due to a high-fat diet (metabolic endotoxemia) .
Bacteroidetes vs Firmicutes – The Obese vs Lean Link?
Bacteroidetes and Firmicutes phyla (groups) comprise ~90% of the human gut bacteria .
In one small study, Bacteroidetes positively correlated with weight loss in obese humans .
A larger study in humans found that obesity was indeed associated with :
- reduced levels of Bacteroidetes
- reduced bacteria density
- more bacteria genes that metabolize carbohydrates and fats for energy
Studies in mice and rats also confirmed the link between Bacteroidetes and leanness. Bacteroidetes are also more abundant in lean animals, while Firmicutes are more abundant in their obese counterparts [20, 21, 22]. However, in these studies, it was unclear whether the obesity-inducing high fat diet caused the bacteria predominance or the bacteria caused the obesity.
Interestingly, mice that have 2 copies of the leptin gene also have a 50% reduction in Bacteroidetes , suggesting that obesity may also change the gut bacteria composition.
Note: Lactobacilli, Streptococci, and Staphylococci are Firmicutes, whereas Bifidobacteria are actinobacteria, which are neither Firmicutes or Bacteroidetes.
Although a number of Firmicutes (like lactobacilli) in the gut seems to correlate with obesity, in many cases, supplementation with Lactobacilli helped with weight loss.
Probiotic Strains for Weight Loss and Metabolic Health
Consuming probiotics can 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 .
Mixed Probiotic Blends and Weight Loss
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 .
In obese children, the intake of synbiotics (probiotics + prebiotics) resulted in a significant reduction in BMI, waist circumference, and some cardiometabolic risk factors, such as total cholesterol, LDL-cholesterol, and triglycerides .
Several studies have demonstrated that individual probiotic bacteria strains can help with weight loss. However, many of these are observational in nature, while others were done in animals.
Probiotic and Weight Loss Tested in Humans
Bifidobacterium animalis and Weight
Daily ingestion of milk containing B. animalis ssp. lactis significantly reduced the BMI, total cholesterol, low-density lipoprotein, and inflammatory markers in humans .
Bifidobacterium breve (B-3) Improves Metabolism and Reduces Belly Fat
B. breve lowered fat mass and improved GGT and hs-CRP in adults with obese tendencies .
- decreased body weight
- reduced waist and hip circumference
- reduce belly fat and fat under the skin in adults with obese tendencies
However, constant consumption of this probiotic may be required to maintain this effect .
Lactobacillus paracasei Reduces Food Intake and Body Weight
L. paracasei decreases energy/food intake in both humans and animals .
Water extract of L. paracasei reduced body weight in obese rats. It decreased the formation of lipid plaques in the aorta, reduced fat cells size, and inhibited fat absorption, thereby reducing fat production (lipogenesis) .
Lactobacillus Plantarum (PL60 and PL62) Burns Fat
L. Plantarum PL60 and PL62 produce a fatty acid called conjugated linoleic acid (CLA), which can help increase fat burning in mice. After 8 weeks of feeding, L. rhamnosus PL60 reduced body weight without reducing caloric intake as well as white fat tissues [40, 41].
Lactobacillus rhamnosus (CGMCC1.3724) 
- induced weight loss
- reduce fat mass
- reduces circulating leptin concentrations
- improved liver parameters in obese children with liver dysfunction noncompliant with lifestyle interventions .
Lactobacillus salivarius Ls-33 Shifts the Microbiota Towards Lean Bacteria 
In obese adolescents, introducing L. salivarius Ls-33 increases groups of bacteria, like Bacteroidetes to Firmicutes ratio.
Clostridium butyricum (CGMCC0313.1, tested in mice)
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 .
Probiotics Associated with Weight Gain
Avoid these if you are trying to lose weight :
- Lactobacillus acidophilus – in both humans and animals
- Lactobacillus fermentum – in animals
- Lactobacillus ingluviei – in animals
- Lactobacillus reuteri – in humans, although it helps with some obesity-related symptoms .
- Raw Probiotics (Amazon or iHerb)
- Probiotic-10 (Amazon or iHerb)
- Flora Probiotic (Amazon or iHerb)
- S Boulardii (Amazon or iHerb)
- L. Acidophilus (Amazon or iHerb)
- L. gasseri (Amazon or iHerb)
- B. bifidum (Amazon or iHerb)
This section contains sponsored links, which means that we may receive a small percentage of profit from your purchase, while the price remains the same to you. The proceeds from your purchase support our research and work. Thank you for your support.
For technical information, check individual probiotic chapters:
- B. animalis (B. lactis)
- B. bifidum
- B. breve
- B. coagulans (L. sporogenes)
- B. longum
- B. subtilis
- C. butyricum
- L. acidophilus
- L. brevis
- L. casei
- L. crispatus
- L. delbrueckii (L. bulgaricus, L. lactis)
- L. fermentum
- L. gasseri
- L. helveticus
- L. johnsonii
- L. lactis
- L. paracasei
- L. plantarum
- L. reuteri
- L. rhamnosus
- L. salivarius
- P. freudenreichii
- S. boulardii
- S. cerevisiae
- S. thermophilus