Review: Studies Reveal Probiotics for Weight Loss

Most of us are guilty of over-eating during the holidays. Surprisingly, taking probiotics may actually help tackle those last pounds and normalize your metabolism. The clinical evidence looks very good so far.

Probiotics for Weight Loss?

At first glance, the idea of using probiotics for weight loss may seem strange, it really isn’t though when you think about the huge contribution gut bacteria play in our digestion. The intestinal microbiota (the total sum of microbial species that live in the intestines) regulates our ability to obtain energy from normally indigestible food1. Some microbial residents produce enzymes that breakdown indigestible carbohydrates. When they do this, they produce nutrient molecules like short chain fatty acids, as by-products that we can digest. Besides being important on a purely digestive level, they also can modulate the functions of neighboring cells and bacteria.

There are several main mechanisms that probiotics may employ to reduce obesity2:

  • Induction of conjugated linoleic acid, which is known to lower weight gain in animals
  • Decrease of circulating leptin, which is produced by fat cells and controls appetite.
  • Increase of brown tissue thermogenesis, which is the creation of heat by burning fat.
  • Reductions in the absorption of lipids
  • Altered activity in appetite centers
  • Altering fasting-induced adipose factor, which regulates lipid metabolism1.

The fact that the microbiota regulate weight and metabolism has also been elegantly proved in experiments using germ-free mice that lack intestinal bacteria. When these mice are given a new microflora, by way of fecal microbiota transfer from obese and lean donors; mice given obesity-associated microbiota become overweight, while the lean donor bacteria keeps the mice thin1.

In a roundabout manner, the meat industry has known for quite a long time that bacteria are important for weight regulation. Many animals raised for meat are given antibiotics. The main reason is to control infectious disease, however, there is also a second reason: antibiotics appear to increase weight gain1, which is advantageous from an economic stand-point. The relationship between antibiotics and weight gain has been well-documented in animal studies1. Interestingly, antibiotic studies in humans have also shown similar effects1.

Obesity and Microbiota

In the last five years, probiotics for weight control has become increasingly interesting to researchers, and a number of investigations into the intestinal bacteria associated with obesity have been published. In general, obesity is reported to be associated with a rise in bacteria derived from the phylum Firmicutes1, 2 while increases in the phylum Bacteroidetes are associated with weight loss in mice1. In humans, the roles of Firmicutes and Bacteroidetes are confusing, and not all of the studies agree. Some of the confusion arises from the fact that genera within Firmicutes include both pro- and anti-obesity species1. This is the case with the well-known gerera Lactobacillus2. A number of studies have tried to circumvent this problem by looking for changes at a species level1, however, there is limited consensus between these studies as well. Environmental, dietary and genetic differences associated with human populations have huge impacts on the composition and function of intestinal microbiota, making these studies difficult to compare.

Fighting Obesity with Probiotics

Despite the confusion about microbiota and obesity, there is information about which probiotic strains one could use to lose weight. A recent meta-study (study using data from multiple trials in humans and mice) found that the most interesting probiotic species for weight loss were Lactobacillus gasseri, L. plantarum and Bifidobacterium animalis; while the species associated with weight gain were L. acidophilus, L fermenteum and L. ingluviel3.

Since this pivotal meta-study, a number of newer human trials have been published. One used a synbiotic mixture and two used L. gasseri strains:

The synbioric mixture was a commercial product, Protexin Balance Plus, which contains various bacteria, a prebiotic and a few vitamins. It was given to obese children for eight weeks. After this period, obesity and metabolic parameters were compared to starting values. The probiotic treated group saw significant improvements for BMI, waist circumference and lipid levels4. This formulation, without the additional vitamins, can be found as Protexin Balance on Amazon.

Lactobacillus gasseri was further examined in two studies: one in Japan and the other in Korea. The studies confirmed the conclusions of the meta-study. Obese volunteers in both countries noticed significant improvements over time. In particular, there was a loss of visceral fat that resulted in reduced waist circumferences5, 6. In the Japanese study, they noted that the positive changes were lost after volunteers stopped taking the supplement. This would imply that you should keep ingesting probiotics to see effects.

Where Is Lactobacillus Gasseri?

If you are thinking of experimenting, L. gasseri seems to be the best bet based on the evidence. Realize, however, that the effects probably won’t be dramatic. Also, there is also the strain limitation. The studies use specific strains: SBT2055 in Japan and BNR17 in Korea. What is widely available is the strain KS-13, which is also known as PA 16/87. This strain is found always in combination with strains of B. bifidum and B. longum. This trio originated in Japan and was sold by the Wakunaga company8. In America, they were initially marketed by the Kyolic brand, which is part of Wakunaga of America9. There are studies that inicate that this trio may be beneficial for the common cold10. Their product is Kyo-Dophilus Digestion and Immune Health.

Suspiciously, products with this particular strain of L. gasseri have the statement, “formally called L. acidophilus.” This, of course, sounds a little disturbing for those searching for L. gasseri and avoiding L. acidophilus. Incidentally, L. gasseri is very similar to L. acidophilus, and it wasn’t recognized as a unique species until Dr. F. Gasser analyzed the DNA in 196811. Although I was unable to determine when the strain L. acidophilus KS-13 became officially L. gasseri KS-13, it is not likely that this change is a marketing strategy. It is more likely that the misidentification was corrected when the strain was analyzed using modern DNA sequencing techniques.

Nowadays, there is a flood of products containing this Japanese trio, and they include the Nature Made Triple Probiotic and Phillips Colon Health. There are also other probiotic supplements that contain L. gasseri combined with many other bacteria species (iFlora, Omnilact). The problem with these mixtures is that they often contain L. acidophilus and L. fermenteum, which were associated with weight gain.

For those living in Europe, another option is a German product called Omniflora N, which can be obtained at This product contains both L. gasseri and B. longum. If other options arise, I will be sure to mention them here.

Good luck with your weight loss program! Even though it’s unlikely that probiotics are a magic bullet for obesity, they still may give you that little extra edge to help you keep your New Year’s resolution.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment.


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11.       Gasser F, Mandel M. Deoxyribonucleic acid base composition of the genus Lactobacillus. J Bacteriol 1968; 96(3): 580-588.