Probiotics for Weight Loss: Separating Fact From Fiction

With growing levels of obesity internationally, largely due to the widespread adoption of the Western diet, it is no surprise that researchers worldwide have been exploring measures to address this extensive public health concern. Probiotics are thought to positively influence gut health, affecting metabolism, fat storage, and overall weight management. Whilst some of the data is promising, research remains ongoing, and it is important to separate fact from fiction.

What are probiotics?

According to The International Scientific Association for Probiotics and Prebiotics, probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”

Probiotics are the ‘good bacteria’ (or yeast) that may typically be found in a number of fermented foods, such as kefir, sauerkraut, kimchi, and yogurt, but may also be taken as a dietary supplement. Probiotic supplementation includes the use of tablets, capsules, liquids, or powders that contain specific probiotic strains.

These ‘good bacteria’ work mainly in the digestive tract, where they affect the body’s gut microbiome. They have also been linked to a range of potential health benefits, including support for digestive health and immune system and even contribution to nervous system function.

Do probiotics help with weight loss?

Probiotics have shown some promise in helping to address weight loss, however, the evidence is inconclusive, and results vary depending on the specific strain and individual and lifestyle factors. Probiotics influence a healthy gut microbiome, which in turn plays a role in the digestive system, metabolism, fat storage, insulin resistance, and appetite regulation, all of which may have an influence on body weight regulation.

Let’s break that down further. These live microorganisms assist in breaking down and fermenting dietary fibers, synthesizing certain essential nutrients, and inhibiting harmful pathogens, all of which are closely linked to digestive health and metabolism. The breakdown of dietary fibers and other carbohydrates by gut bacteria produces short-chain fatty acids (SCFA), which support the body's overall metabolism, including fat metabolism, and may also potentially contribute to the management of appetite-controlling hormones within the body.

Probiotics, due to short-chain fatty acid production, may help reduce chronic low-grade inflammation in the gut, which is linked to both obesity and metabolic-related diseases due to potential gut microbiome imbalance. That being said, human studies are limited to establishing a definitive causal relationship between SCFA production by probiotics and fat metabolism, as most current evidence is based on animal models.

Gut and weight connection

Growing research suggests there may be additional links to weight, including the gut microbiomes’ ability to regulate energy extraction from food, with certain strains linked to greater energy retention and fat absorption. The Firmicutes/Bacteroidetes ratio is frequently cited within scientific literature as a 'hallmark of obesity.'

Some studies describe the gut microbiota of animals and humans with obesity exhibit a higher Firmicutes/Bacteroidetes ratio compared to other individuals. However, this relationship is still not fully understood and remains the subject of much debate. While these bacteria are essential to the human gut microbiome and contribute positively to digestive and metabolic functions, dysbiosis (an imbalance in their levels) may negatively impact such areas within the body. One particular systematic review concludes that gut dysbiosis plays a crucial role in the development of a number of obesity-related metabolic abnormalities, including type 2 diabetes and cardiovascular disease.

Separating fact from fiction: common myths about probiotics

In order to determine the truth behind the use of probiotics for weight loss, we must first consider common myths.

Myth 1: probiotics are a quick fix for weight loss

Regardless of the research, it is extremely important to note that probiotics alone are not guaranteed to help you lose weight. Not only is more research needed to confirm any links in this area, but probiotics should only ever be used in conjunction with a healthy, well-balanced diet alongside regular physical activity. They are by no means a magic solution for weight loss.

Myth 2: probiotics work the same for everyone

The effects of probiotics vary considerably based on individual factors such as genetics, baseline nutritional status, age, level of physical activity, eating disorders, and existing gut flora. While certain strains of probiotics may have a beneficial effect on weight management for some people, this cannot be replicated in everyone, and more research is needed to determine the full extent of probiotics’ role in weight loss.

Myth 3: all probiotic strains are equal for weight loss

Not all strains of probiotics have the same impact on weight loss, and some strains may be more beneficial for gut health or weight management than others. Interestingly, some probiotics, such as strains of Lactobacillus species, have actually been linked to weight gain.

Choosing the right probiotic

The strain of probiotics being used has an effect on the potential results. It is extremely important to tailor your probiotic choice to align with your personal health goals, be it supporting your immunity, contributing to the reduction of digestive issues, or weight management. A healthcare professional may help to advise you on the appropriate strains of probiotics for your needs based on evidence from clinical trials.

Key probiotic strains for weight loss

Certain probiotic strains are more commonly understood to support weight loss, like Bifidobacterium spp. and Lactobacillus spp.

In a 12-week double-blind, placebo-controlled clinical trial, a multi-strain probiotic capsule containing a combination of Bifidobacterium and Lactobacillus strains contributed to the reduction of BMI, body weight, and waist-to-hip ratio in overweight and obese adults, alongside no specific dietary or exercise modifications.

Lactobacillus gasseri showed a decrease in body fat percentage, BMI, waist circumference, and areas of visceral and subcutaneous fat in a multi-center, double-blind, parallel-group randomized controlled trials conducted with 210 healthy adults with large areas of visceral fat.

A systematic review found that certain strains, specifically Lactobacillus gasseri, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus curvatus, used alongside or with species from the Bifidobacterium genus, have the potential to support weight loss in overweight and obese individuals.

While these probiotic strains show promise for weight loss, long-term studies remain scarce, indicating that the observed effects may only be short-term. Additionally, there is considerable variability among these studies in terms of underlying protocols and research methodologies, which complicates the ability to reliably conclude the weight loss benefits due to inconsistent findings across different research studies.

Probiotic dose and potency

Probiotics are measured in colony-forming units (CFUs), which indicate the number of viable cells. A larger number of CFUs is often marketed as a reflection of the product's quality and effect, with the average CFU count typically within the range of 1–10 billion per serving.

Always look for products labeled with the number of CFU at the end of the product’s shelf life, not at the time of manufacture, as live bacterial viability may decrease during ongoing shelf life.

Ensuring your probiotic is stored correctly based on manufacturer guidance can help to maintain such potency.

Although this is an important consideration, your choice of strain and product should be based on data from clinical research, as indicated for your individual health needs. Correct dose and guidance for use should be determined through the advice of a healthcare professional.

Final thoughts

Probiotics have been linked to weight loss due to their role in influencing the body’s gut microbiota, with certain strains such as Lactobacillus and Bifidobacterium thought to support digestion and metabolism. However, the effects of probiotics for weight management may vary depending on a person’s age, baseline nutritional status, individual factors, and the particular strain being used.

Probiotics cannot replace a healthy, balanced diet alongside regular physical activity and exercise for weight management. It is extremely important to consult with a healthcare professional before starting any new supplement regimen, especially in the context of pre-existing health conditions and existing medications.