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Obesity, Anorexia, Diet, and the Microbiome


The gut microbiome has been shown to have a major impact on food cravings, satiety, processing of nutrients, and determining what our body does with those nutrients. FMTs (Fecal Microbiota Transplants) have been shown to be able to transfer obesity in animal models, but more human studies are needed.


Review, 2018: Importance of gut microbiota in obesity "the increase in fat mass is not only due to a more efficient harvest of energy, but also the microbiota participates in changes in endotoxemia, bowel permeability, insulin resistance, hormonal environment, expression of genes regulating lipogenesis, interaction with bile acids, as well as changes in the proportion of brown adipose tissue, and effects associated with the use of drugs such as metformin"

Review, 2018: Gut Microbes and Health: A Focus on the Mechanisms Linking Microbes, Obesity, and Related Disorders:

Review, 2018: Insights into the role of gut microbiota in obesity: pathogenesis, mechanisms, and therapeutic perspectives:

Review, 2017: Fecal microbiota transplantation in metabolic syndrome: History, present and future

Review, 2017: Influence of diet on the gut microbiome and implications for human health

Review, 2016: Treating Obesity and Metabolic Syndrome with Fecal Microbiota Transplantation

Review, 2012: Impact of the Gut Microbiota on the Development of Obesity: Current Concepts:


Recent data show a link between the diversity and richness of gut microbiota and the way we store fat, how we regulate digestion hormones and blood glucose levels, and even what types of food we prefer (Aug 2017):

Study suggests bacteria in the gut has a greater influence on body fat compared to diet. Dissecting the role of the gut microbiota and diet on visceral fat mass accumulation (Jul 2019, 1760 female twins)

A single genetic change in gut bacteria alters host metabolism via microbial enzymes impacting bile metabolism (2018):

Human gut microbiota after bariatric surgery alters intestinal morphology and glucose absorption in mice independently of obesity (Aug 2022)

Host genotype affects the abundance of taxa associated with metabolic disease. Gut microbiota affects susceptibility to diet-induced metabolic disease. The gut microbiome modulates insulin secretion (Feb 2017):

Long term but not short term exposure to obesity related microbiota promotes host insulin resistance (Nov 2018):

Study Links BMI, Lipid Levels to Gut Microbes (Sep 2015). || Including fungal mycobiota (Oct 2015):

Fat and thin people have different gut bacteria: (Oct 2018) - (Sep 2016)

Heritable components of the human fecal microbiome are associated with visceral fat (Sep 2016): | Maternal prepregnancy obesity may imprint a selective gut microbial composition during late infancy with distinct functional performances (Aug 2017):

Dysosmobacter welbionis is a newly isolated human commensal bacterium preventing diet-induced obesity and metabolic disorders in mice (Jun 2021)

Cross-talk between Akkermansia muciniphila and intestinal epithelium controls diet-induced obesity (May 2013)

A purified membrane protein from Akkermansia muciniphila or the pasteurized bacterium improves metabolism in obese and diabetic mice (Nov 2016):

An intestinal microbiota-farnesoid X receptor axis modulates metabolic disease. Mice lacking expression of FXR in the intestine were resistant to (High Fat Diet)HFD-induced obesity, insulin resistance and NAFLD thus confirming that intestinal FXR is involved in the potentiation of metabolic disease (Sep 2016): || Gut microbiota, FXR, and bile acids as regulators of host metabolism (Feb 2017):

Dual-specificity phosphatase 6 deficiency regulates gut microbiome and transcriptome response against diet-induced obesity in mice (Nov 2016):

Short Chain Fatty Acids Prevent High-fat-diet-induced Obesity in Mice by Regulating G Protein-coupled Receptors and Gut Microbiota (Nov 2016):

Mendelian Randomization Analysis Reveals Causal Effects of the Human Gut Microbiota on Abdominal Obesity (Mar 2021, n=1126 twin pairs)

TED talk by microbiome researcher, Rob Knight (obesity part around 11:30):

Cravings, satiety, and diet:

Recent data show a link between the diversity and richness of gut microbiota and the way we store fat, how we regulate digestion hormones and blood glucose levels, and even what types of food we prefer (Aug 2017):

Gut flora manipulate (through the vagus nerve) their host's eating patterns & cravings, behavior & mood, taste receptors, and more (Aug 2014):

Host Genetic Background and Gut Microbiota Contribute to Differential Metabolic Responses to High Fructose Consumption in Mice (2018):

Gut bacteria can help to predict how the body will respond to fatty foods. Chemical signatures from gut bacteria which show up in urine can be used to predict how the body will respond to a 'junk' diet. (July 2017)

Gut microbiota predicts body fat change following a low-energy diet: a PREVIEW intervention study (May 2022, 2224 adults)

Dietary modulation of gut microbiota contributes to alleviation of both genetic and simple obesity in children (Jul 2015):

Nutrient poor environment causes bacteria to adapt, this causes host to store more fat. Direct communication with mitochondria (Apr 2017):

Dietary fat and gut microbiota interactions determine diet-induced obesity in mice (& difference between animal fat & vegetable fat) (Oct 2016)

Effect of diet soda on gut bacteria (Sep 2014):

Artificial sweeteners induce glucose intolerance by altering the gut microbiota (Sep 2014): | And block enzyme activity (Nov 2016): | Artificial Sweeteners May Change Our Gut Bacteria in Dangerous Ways (Apr 2015):

Changes in the microbiome may contribute to cognitive changes associated with eating a Western diet (May 2016, mice):

Effects of Gut Microbes on Nutrient Absorption and Energy Regulation (Feb 2012):

Starving our Microbial Self: The Deleterious Consequences of a Diet Deficient in Microbiota-Accessible Carbohydrates (Aug 2014):

The Effect of Diet on the Human Gut Microbiome: A Metagenomic Analysis in Humanized Gnotobiotic Mice (Nov 2009):

Diet rapidly and reproducibly alters the human gut microbiome (Dec 2013):

Resistant Starch Alters the Microbiota-Gut Brain Axis: Implications for Dietary Modulation of Behavior (Jan 2016): - (Feb 2016, rats):

Fast food fever: reviewing the impacts of the Western diet on immunity. Dietary impact on the gut microbiome and the mechanisms by which our poor dietary choices are encoded into our gut, our genes, and are passed to our offspring (Jun 2014):

Diet-induced extinctions in the gut microbiota compound over generations (Jan 2016):

Fecal Microbiota Transplant (FMT):

Review, 2023: Fecal microbiota transplantation in obesity metabolism: a META analysis and systematic review

Anorexic patient recovers thanks to fecal transplant in Jiangsu China. A 26-year-old woman who was dying due to excessive weight loss recently pulled through after receiving an FMT (Nov 2023)

Doctors call for fecal transplant regulation after seeing unexpected results (obesity transfer in people) (Feb 2015): -

Transfer of Obesity via the Gut Microbiome is Mediated Specifically through Suppression of Non-Aerobic Resting Metabolism (Apr 2015): || Researchers find it's not just the bacteria that could produce this effect. Transferring just the bacteriophage was sufficient to reduce resting metabolic rate and cause weight gain in control mice (Nov 2015):

When researchers in China took a strain of E. cloacae (B29) from the gut of a volunteer who weighed in at 385 pounds and transplanted it into germ-free mice, the rodents themselves then became obese compared to similar mice fed an identical diet, but without the E. cloacae (Dec 2012): -

Freeze-dried poop pills being tested for obesity treatment (Jan 2016):

The gut microbiota affects calorie harvest and energy homeostasis. Germ-free mice have 40% less total body fat than conventional mice although they ingest 29% more calories than their conventionally raised littermates. Fecal microbiota transplanted from conventionally raised mice to germ-free mice triggered a 57 % increase in the amount of body fat and a dramatic increase in hepatic triglyceride levels and insulin resistance without modifying the amount of food consumed (Apr 2016): || Germ-free lab mice also suffer various problems: - (Oct 2016)


Children who take antibiotics gain weight faster (Oct 2015, n=163,820): - (Mar 2016, n=21,714) - (Jul 2016, n=979) - (Mar 2017, n=162) || Also seen in feed animals (along with pro & pre biotics) (Nov 2016):

Testosterone disruptor effect and gut microbiome perturbation in mice: Early life exposure to doxycycline (Jan 2019): "Early-life exposure to low-dose of doxycycline associates with increased risk of obesity."

Immune system:

Immune system defects seem to contribute to obesity in mice. T cell–mediated regulation of the microbiota protects against obesity (July 2019) "healthy mice have plenty of Clostridia—a class of 20 to 30 bacteria—but those with an impaired immune system lose these microbes from their gut as they age. Even when fed a healthy diet, the mice inevitably become obese. Giving this class of microbes back to these animals allowed them to stay slim"

Adenovirus 36 and Obesity: An Overview (2015):

The Inhibitory Innate Immune Sensor NLRP12 Maintains a Threshold against Obesity by Regulating Gut Microbiota Homeostasis (2018):

Gut intraepithelial T cells calibrate metabolism and accelerate cardiovascular disease (Jan 2019): "Integrin β7− mice that lack natural IELs are metabolically hyperactive and, when fed a high-fat and high-sugar diet, are resistant to obesity, hypercholesterolaemia, hypertension, diabetes and atherosclerosis"

The gut microbiota regulates white adipose tissue inflammation and obesity via a family of microRNAs expressed in adipocytes (fat cells) (June 2019) - How a Disturbed Gut Microbiome May Dysregulate Fat Tissue in Obesity (2 of 2) (image)


Review, Jan 2019: A new review calls for the gut microbiome to be considered as part of standard nutritional rehabilitation for anorexia nervosa. The gut microbiome in anorexia nervosa: relevance for nutritional rehabilitation -

Review, Feb 2019: Can Gut Microbiota and Lifestyle Help Us in the Handling of Anorexia Nervosa Patients?

Review, Feb 2019: The Impact of Starvation on the Microbiome and Gut-Brain Interaction in Anorexia Nervosa

The gut microbiota contributes to the pathogenesis of anorexia nervosa in humans and mice (Apr 2023, n=147) "we performed faecal microbiota transplantation from AN cases to germ-free mice"

The gut microbiome derived from anorexia nervosa patients impairs weight gain and behavioral performance in female mice (Aug 2019) "decreased appetite as well as the capacity to convert ingested food to unit of body substance may contribute to poor weight gain"

Conflicting data:

Gut microbial communities from patients with anorexia nervosa do not influence body weight in recipient germ-free mice (Mar 2021)