Can probiotics help with weight loss?

Weight loss is not an easy thing to get right, and whilst diet and physical exercise play a big role, health professionals and researchers agree that it’s much more complex than that, with inflammation, hormone imbalance, genetics, and other factors contributing to individuals’ struggles with weight. But have you ever considered that your gut could be playing a part on your weight loss journey? Research shows that reduced bacterial diversity is strongly associated with weight gain and obesity,[i] and that supporting a healthy gut, and using probiotics could promote weight loss through a variety of mechanisms.

So, how do gut bacteria affect weight?

The gut contains trillions of bacteria, beneficial and pathogenic, which work together to support overall health and fight off infections. These microbes all have particular roles and collectively play a huge role in overall health. A pioneering study from 2016 displays the influence of microbial composition through faecal transplants in mice, where lean mice were given a faecal microbial transplant (FMT) from obese mice, resulting in increased adiposity and weight. Furthermore, when obese mice were given faecal transplants from lean mice, there was an increase in indigestible fibre fermentation, and a decrease in weight and body fat.[ii] This study perfectly illustrates the dramatic capacity that our gut bacteria holds over our ability to lose weight, which has lead FMT to be suggested as a potential treatment for obesity.[iii]

Gut microbes heavily influence our energy metabolism by controlling the extraction of energy from the food we eat, carbohydrate fermentation, and regulation of gut hormones (e.g. glucagon-like peptide 1, leptin) which are involved in energy metabolism and appetite, consequently affecting our weight. [iv] This relationship between energy harvesting and energy metabolism is still being researched. However, we do know that there is an increase in energy extraction efficiency in obese individuals and reduced carbohydrate fermentation.[v] These microbes further influence weight by promoting glucose absorption in the gut and increasing inflammation, all associated with obesity. [vi] Reduced microbial diversity is associated with increased gut permeability, which in turn increases blood levels of a bacteria-derived toxin called lipopolysaccharide (LPS). LPS has been strongly linked with obesity. It mainly works by triggering whole body inflammation and oxidative stress, leading to poor glucose management, insulin resistance, and fat accumulation.[vii]

So can taking probiotics support weight loss? There are a number of studies assessing the effect of probiotics, mainly using various combinations of Lactobacillus and Bifidobacterium strains, which show a positive effect on weight loss by reducing inflammation and gut permeability,[viii] as well as improving glucose management.[ix] Another review has also demonstrated beneficial effects of probiotics, especially Lactobacillus, on diabetes and related metabolic parameters.[x]

The Right Balance - The Firmicutes:Bacteroidetes Ratio

Composition of the microbiota further depends on the type and ratio of bacteria that are present in the gut. There are 5 different families of bacteria within the gut, known as phyla. The 2 most dominant phyla of bacteria are Firmicutes and Bacteroidetes, predominantly found in the large intestines. The ratio of these particular bacterial strains can help regulate whether you put on weight easily, or whether you have a more slender body type, by influencing the extraction of energy from food.[xi] Current research suggests that higher levels of Firmicutes and lower levels of Bacteroidetes in the gut are seen in obesity.[xii] Although not all research is concordant with this, and some studies have found no correlation between this ratio and obesity, we do know that reduced microbial diversity is highly connected to obesity.[xiii]

Since we now know that the diversity of the gut microbiome is a major factor to consider with weight loss, let’s address some of the common factors that can negatively impact it:

• Diet, specifically low in fibre and/or high in refined sugar and fat,[xiv] has been found to alter microbial diversity and induce low-grade inflammation, further increasing gut permeability. High fat and high sugar diets specifically can increase the Firmicutes:Bacteroidetes ratio.[xv]
• Stress has a direct impact on the gut microbiome, disrupting the microbial balance and encouraging gut permeability and inflammation,[xvi] and in turn, can promote metabolic dysfunction, such as obesity.[xvii]
• Antibiotics - a recent article published in the World Journal of Pediatrics illustrates a correlation between frequent antibiotics use in childhood and an increased risk of obesity.[xviii] Antibiotic use has also been shown to lead to an imbalance in Firmicutes and Bacteroidetes, further altering the microbiome.[xix]

Prebiotic fibre and weight loss

Prebiotic fibre is found in plants, particularly foods such as onions, garlic, and leeks. These are known as indigestible fibres. They cannot be broken down by our digestive enzymes, so they reach the colon intact where they are fermented by our gut bacteria. This fermentation process produces short chain fatty acids (SCFAs); acetate, propionate, and butyrate, which positively impact the gut barrier and our metabolism.[xx] The more abundant and diverse the supply of prebiotic fibre through diet, the more abundant and diverse the gut microbiome.[xxi] Robust production of SCFAs by our colonic bacteria has been shown to protect against weight gain and obesity.[xxii]

Clinical evidence even indicates that a type of prebiotic called inulin can increase satiety by modulating hormones involved in regulating appetite.[xxiii] In fact, there is an abundance of research to show that an increased dietary fibre intake, preferably the indigestible type, can decrease feelings of hunger.[xxiv] This could lead to reduced calorie intake and less snacking, which can then further support weight loss. Research on fibre intake is often based on large doses of a single type of prebiotic fibre. However, what’s important is to increase the total amount of fibre generally in your diet, of different types from a variety of foods. Some estimates suggest we aim for at least 30g/day to help reduce body fat percentage and weight gain.[xxv]

Summary

Increasing evidence suggests that associations exist between our gut microbiome and other metabolic factors linked to weight gain and obesity.[xxvi] Modulating our gut microbiome through probiotics and prebiotics, and reducing our exposure to the various factors which can negatively impact it (e.g. stress, antibiotics), can be an effective tool when looking to holistically support weight management.

If you’re struggling with weight loss and would like tailored advice to suit your needs, please contact our Clinical Nutrition team.

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References

[i] Turnbaugh PJ et al. A core gut microbiome in obese and lean twins. Nature. 2009; 457(7228);480-484.

[ii] Ridaura V et al. Cultured gut microbiota from twins discordant for obesity modulate adiposity and metabolic phenotypes in mice. Science. 2013; 341(6150); 1-14.

[iii] Lee P et al. Gut microbiota and obesity: An opportunity to alter obesity through faecal microbiota transplant (FMT). A J of Pharma and Therapeutics. 2018; 21(3); 479-490.

[v] Menni C et al. Gut microbiome diversity and high-fibre intake are related to lower long-term weight gain. Int journal of obesity. 2017; 41;1099-1105.

[vi] Cani P et al. Involvement of gut microbiota in the development of low-grade inflammation and type 2 diabetes associated with obesity. Gut microbes. 2012; 3(4); 279-288.

[vii] Brusaferro A et al. Is It Time to Use Probiotics to Prevent or Treat Obesity? Nutrients. 2018; 10(11): 1613.

[viii] Roberts, J.D, et al. An Exploratory Investigation of Endotoxin Levels in Novice Long Distance Triathletes, and the Effects of a Multi-Strain Probiotic/Prebiotic, Antioxidant Intevention. Nutrients, 2016; 8 (11): 733

[ix] Brusaferro A et al. Is It Time to Use Probiotics to Prevent or Treat Obesity? Nutrients. 2018; 10(11): 1613.

[x] Razmpoosh E et al. Probiotics as beneficial agents in the management of diabetes mellitus: a systematic review. Diabetes Metab Res Rev. 2016; 32: 143–168.

[xi] Turnbaugh PJ et al. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature. 2006. 444;1027-1031.

[xii] Pray L et al. Influence of the Microbiome on the Metabolism of Diet and Dietary Components. National Institute of Health. 2013; 1-179.

[xiii] Murphy E et al. Influence of High-Fat-Diet on Gut Microbiota: A Driving Force for Chronic Disease Risk. Curr opin Clin Nutr Metab Care. 2015; 18(5); 515-520.

[xiv] Kobyliak N et al. Probiotics in prevention and treatment of obesity: a critical review. Nutr Metab. 2016; 13:2-14.

[xv] Murphy E et al. Influence of High-Fat-Diet on Gut Microbiota: A Driving Force for Chronic Disease Risk. Curr Opin Clin Nutr Metab Care. 2015; 18(5); 525-520.

[xvi] Karl J et al. Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota. 2018; 9;1-32.

[xvii] Liu, T. The microbiome as a novel paradigm in studying stress and mental health. The American psychologist. 2017; 72(7); 655-667.

[xviii] Kelly D et al. Antibiotic use in early childhood and risk of obesity: longitudinal analysis of a national cohort. World J Pediatr. 2019; 15(4); 390-397.

[xix] Rinniella E et al. What is the health gut Microbiota Composition? A changing ecosystem across Age, Environment, Diet and Disease. Microoganisms. 2019; 7(1); 1-14.

[xx] Sonnenberg E & Sonnenberg J. Starving our Microbial Self: The Deleterious Consequences of a Diet Deficient in Microbiota-Accessible Carbohydrates. Cell Metabolism. 2014; 20(5);779-786.

[xxi] Roberfroid M et al. Prebiotic effects: metabolic and health benefits. Br J Nutr Suppl. 2010; 104(2);1-93.

[xxii]Byrne C et al. The role of short chain fatty acids in appetite regulation and energy homeostasis. 2005; 39(9); 1331-1338.

[xxiii] Guess et al.A randomized controlled trial: the effect of inulin on weight management and ectopic fat in subjects with prediabetes. Nutrition & Metabolism. 2015; 12: 36

[xxiv] Salvin J & Green H. Dietary fibre and satiety. Br Nutr Foundation. 2007; 32(1);32-42.

[xxv] Babiker et al. Effects of gum Arabic ingestion on body mass index and body fat percentage in healthy adult females: two-arm randomised, placebo controlled, double-blind trial. Nutr J. 2012; 11:111

[xxvi] Hanley AJ, Festa A, D’Agostino Jr RB, Wagenknecht LE, Savage PJ, Tracy RP, et al. Metabolic and inflammation variable clusters and prediction of type 2 diabetes: factor analysis using directly measured insulin sensitivity. Diabetes. 2004;53:1773–81