Weight and the Gut Microbiome

October 22nd, 2021 | Posted in Info

When to Eat

If you’ve read the blog posts How Much vs What We Eat and Weight Gain and When to Eat you’ll have an insight into the fact that how much we weigh is more complicated than might previously have been thought. This post will look at the role of the gut microbiome in weight.

The human body is host to a vast number of microbes, including bacterial, fungal and protozoal microorganisms, which together constitute our microbiota. Evidence is emerging that the intestinal microbiome is intrinsically linked to overall health, including obesity risk. For example, a study on mice with metabolic syndrome found that particular bacteria were strongly linked to metabolic syndrome with its associated pathologies including weight gain around the middle, high blood pressure and diabetes (1).

The gut microbiota affects host metabolism and obesity through several pathways involving gut barrier integrity, production of metabolites affecting satiety and insulin resistance, epigenetic factors, influencing the amount of energy that is extracted from the diet and altering genes that regulate energy expenditure and storage (2,3).

Weight Loss and the Gut Microbiome

New research suggests that the gut microbiota can help or hinder weight loss. The study found that the ability of the gut microbiome to break down starches was increased in people who did not lose weight. Another key finding was that genes that help bacteria grow faster and multiply were increased in people who lost more weight (4).

Before this study, it was known that the composition of bacteria in the gut was different in obese people than in people who were non-obese. This research shows that there are a different set of genes that are encoded in the gut bacteria that also respond to weight loss interventions. The gut microbiome seems to be a major player in modulating whether a weight loss intervention will be successful or not.

Changing the Microbiome

The good news is that the composition of the gut microbiota is not fixed and can be influenced by what we eat. This means that if someone has gut bacterial genes that make them resistant to weight loss, altering their diet could shift the composition of the microbiome so that it would help them lose weight.

Modulating the composition of the gut microbiota could be done through dietary changes as well as through the consumption of:

1. Probiotics – live microbes that benefit the host.

2. Prebiotics – nondigestible or limited digestible food constituents, such as oligosaccharides, which act as food or fertilisers for the beneficial microbes.

3. Synbiotics – contain both probiotics and prebiotics.

4. Resveratrol – Resveratrol fed to mice on a high fat diet caused a remarkable alteration in microbiota composition and played a key role in controlling obesity development (5).

Faecal transplants are also under investigation in which faeces from a healthy person are transplanted into the bowels of an obese person (2).

While research into the role of the gut microbiome in obesity is in early stages it holds promise in providing us with therapeutic targets that may restore the gut microbiome to a healthy state and help in the prevention and treatment of obesity.


  • P Lu et al. Intestinal epithelial Toll-like receptor 4 prevents metabolic syndrome by regulating interactions between microbes and intestinal epithelial cells in mice. Mucosal Immunology, 2018;
  • CD Davis.The Gut Microbiome and Its Role in Obesity. Nutr Today. 2016 Jul-Aug:51(4): 167-174
  • Lee CJ et al. Gut microbiome and its role in obesity and insulin resistance. Ann N Y Acad Sci. 2020 Feb;1461(1):37-52.
  • Diener C et al. Baseline Gut Metagenomic Functional Gene Signature Associated with Variable Weight Loss Responses following a Healthy Lifestyle Intervention in Humans. MSystems, 2021;
  • Wang P et al. Resveratrol-induced gut microbiota reduces obesity in high-fat diet-fed mice. Int J Obes (Lond). 2020 Jan;44(1):213-225.