The Gut Microbiome Influences Weight

by georgia hartmann

Women’s Health Expert

Over the past decade, the bacteria in the gut (termed gut microbiome) has received considerable attention as a novel factor contributing to the development of weight gain and obesity. This area of research dates back to a ground-breaking study in the early 2000s which showed that obesity could be transferred from one being to another via the gut. Yes, that’s right. Faecal matter from an obese mice was transferred to a germ-free mice, causing it to become obese (despite no change in kilojoule input or output). This has sparked great interest in the link between weight and gut health.[1]

So how does the gut microbiome influence weight gain?

First, weight can be influenced by a lack of diversity in the bacteria living in the digestive system. While defining exactly what constitutes an ‘obese microbiome’ is still being defined (and debated), what we do know is that lower concentrations of Akkermansia muciniphila, bifidobacteria and Faecalibacterium prausnitzii have been observed fairly consistently in obese individuals.[2-5] 

Interestingly, a recent systematic review and meta-analysis out of Norway reported that probiotic supplementation resulted in a significantly greater reduction in body weight, body mass index (BMI), and fat percentage compared with placebo. Another study showed that supplementation with specific strains of Lactobacillus species can decrease body weight and body fat. Though, it is important to know that the beneficial effects of probiotics are strain-specific (meaning that you cannot simply pick up a probiotic off the shelf and expect it to work). For example, when combined with a lower-calorie diet, Lactobacillus plantarum and Lactobacillus rhamnosus have beneficial effects on weight.[6-7]

The gut microbiome also affects metabolism through its production of short-chain fatty acids (SCFAs). In terms of balancing weight, SCFAs are important as they increase fat burning and decrease fat storage. However, for SCFAs to be produced, they need healthy gut bacteria which is dependent upon a number of factors including the amount of fibre in the diet.[8]

Here’s what we know about fibre

Around the globe, a variety of dietary patterns are promoted for weight loss. From a Mediterranean-style diet to a low–glycemic index diet, plant-based diet, high-pulse diet, to a variation of fasting, it can be overwhelming to know where to start. 

What we do know (and what consistently shows up in large prospective cohort studies) is that there is a strong association between fibre intake and body weight. In fact, a recent meta-analysis published in The American Journal of Clinical Nutrition found that consuming a minimum of 6.7g of fiber per day for 10 weeks can reduce body weight, BMI and waist circumference. Considering the recommended daily intake of fibre is 25-30g (and that increasing daily fibre intake to reach this target will only have added benefit), we each need to ensure we include fibre into each meal. Think oats. Think psyllium husk. Think apples. Think vegetables. Think nuts. Think seeds.[9-10] 

[1] Turnbaugh, P.J., et al. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature, 2006. 444(7122). PMID: 17183312.

[2] Turnbaugh, P.J., et al. The core gut microbiome, energy balance and obesity. Journal of Physiology, 2009. 587(Pt 17). PMID: 19491241.

[3] Andoh, A., et al. Comparison of the gut microbial community between obese and lean peoples using 16S gene sequencing in a Japanese population. Journal of Clinical Biochemistry & Nutrition, 2016. 59(1). PMID: 27499582.

[4] Yassour, M., et al.  Sub-clinical detection of gut microbial biomarkers of obesity and type 2 diabetes. Genome Medicine, 2016. 8(1). doi:10.1186/s13073-016-0271-6.

[5] Kalliomaki, M., et al. Early differences in fecal microbiota composition in children may predict overweight. American Journal of Clinical Nutrition, 2008. 87(3). PMID: 18326589.

[6] Borgeraas, H., et al. Effects of probiotics on body weight, body mass index, fat mass and fat percentage in subjects with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. Obesity Reviews, 2018. 19(2). PMID: 29047207.

[7] Crovesy, L., et al. Effect of Lactobacillus on body weight and body fat in overweight subjects: a systematic review of randomized controlled clinical trials. International Journal of Obesity, 2017. 41(11). PMID: 28792488.

[8] Kim, K.N., et al. Short Chain Fatty Acids and Fecal Microbiota Abundance in Humans with Obesity: A Systematic Review and Meta-Analysis. Nutrients, 2019. 11(10). PMID: 31635264.

[9] Jovanovski, E., et al. Can dietary viscous fiber affect body weight independently of an energy-restrictive diet? A systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition, 2020. 111(2). PMID: 31897475.

[10] Miketinas, D.C., et al. Fiber Intake Predicts Weight Loss and Dietary Adherence in Adults Consuming Calorie-Restricted Diets: The POUNDS Lost (Preventing Overweight Using Novel Dietary Strategies) Study. Journal of Nutrition, 2019. 149(10). PMID: 31174214.

women’s  health expert

by georgia hartman

Women’s Health Expert

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