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The gut-obesity connection: how your microbiome may be influencing your weight

The gut-obesity connection: how your microbiome may be influencing your weight

Diets rich in fibre improve gut microbe diversity and work against factors causing obesity, say studies


An illustration of a scientist exploring good bacteria in a gut
Representational image | Shutterstock

One often thinks of obesity as a problem of sustained energy imbalance – the amount of energy taken in through food is greater than the energy expended through activity. However, new research  shows obesity is a far more complex condition that involves several metabolic pathways, with a key factor being the health of the gut microbiome.

From helping break down food to producing neurotransmitters, the colony of bacteria housed in intestines or gut microbiome has become a key area of study in understanding obesity. At the simplest, obese individuals are seen to have guts with lower diversity of beneficial bacteria.

This has prompted researchers to dig into the role of the gut microbiome in the development of obesity.  While there is still a long way to go, scientists say a few things have become clear:

Obesity is not just about food

Obesity is defined as an abnormal or excessive fat accumulation that presents health risks. People who are obese often indulge in carbohydrate-rich foods while not performing any rigorous physical activity. However, diet is not the only factor contributing to obesity, it has a lot to do with the secretion of hormones and immune cells.

Obesity can be present in families due to common genes. The gut microbiome too may be affected by environmental and genetic factors, altering the gut-derived metabolites (such as short-chain fatty acids) that play a crucial role in the body’s regulation of energy and host metabolism.

Diet, still a major factor in obesity

Diet is a major factor in determining the quality of the gut microbiome – what one eats and how the dietary components are metabolised by one’s intestinal bacteria can positively or negatively impact the development of obesity. However, there are other factors that can affect the gut microbiome and increase one’s chances of developing the condition.

“Diet is the main driver in shaping the gut microbiota. However, it is important to point out that disruptions in said microbiota also occur on the basis of different genetic background, physical activity, ageing, overuse of antibiotics, certain medical procedures, and other factors,” Karolline May, postdoctoral researcher at the University of Washington in United States, told Happiest Health.

A diet rich in fibre may favour an abundance of beneficial bacteria in the gut that can reduce the risk of developing obesity. But conversely, diets high in sugar and fats have been found to create imbalances in bacterial populations and therefore contribute to inflammation, which is also observed in obese individuals, she adds.

May’s lab recently showcased this correlation in an animal model. “Our lab at the University of Washington, Seattle, demonstrated that an obesogenic diet (a high-sugar and high-fat diet) decreased bacterial colonic diversity and affected the release of short-chain fatty acids release in genetically modified mice,” she adds.

In other research, data from rodent and human models have shown that the Western diet which is high in sugar and fats can lead to gut dysbiosis, a state that is characterised by an increase in bacterial strains that are deleterious to good health and play a role in the development and progression of obesity.

High-fibre diets as obesity remedies

High-fibre diets   favour the colonisation of the gut with beneficial bacterial populations, which reduces the chance of developing cardiovascular conditions. Scientists say there is strong rationale in eating foods with a lot of fibre to reduce the risk factors associated with obesity.

“A diet rich in vegetables and fibre, such as vegetarian or Mediterranean diets, regulate gut microbiota and manages obesity,” Prof. Amedeo Amedei from the department of experimental and clinical medicine at The University of Florence in Italy, told Happiest Health.

Besides food and changes in diet, a handful of strategies have been used to restore gut microbiota, including the use of probiotics (living bacteria and yeasts), prebiotics (non-digestible dietary fibres and a possible alternative to probiotics), and  synbiotics (a mixture of probiotics and prebiotics).

Therapeutic strategies like pharmaceutical formulas and functional diets (i.e., vegan, gluten-free, and low FODMAP – fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) can  play an important role to manage  obesity.

A human clinical trial by researchers at Harvard University, University of California and Duke University showed that a change in diet to one that is either strictly plant-based or animal-based affect gut microbiota balance after 24 hours. In another human trial, a vegan diet promoted changes in the composition of the gut microbiota followed by positive metabolic responses including weight loss and an increase in insulin sensitivity.

Leptins, sleep, and exercise

Another interesting area of research is on the role of leptin, a protein released by fat cells in the body that help in controlling appetite and fat storage. Obese individuals are seen to have resistance to leptin, making them hungry regardless of the body’s fat stores running full. A leptin resistance is the consequence of consuming food high in calories and deficient in nutrients and thereby crashing the gut microbiota, explains Prof. Amedei.

Moreover, scientists are studying how lifestyle changes can promote better health of the intestinal tract and the trillions of bacteria that live there. They have found that getting a good night’s sleep, exercising regularly, and eating more fiber (vegetables and fruits) can promote the growth of good microbes in one’s gut and prevent many health conditions.

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Challenges still exist

“Research is advised to identify whether these approaches (vegan and other high-fibre diets) are feasible and if they can be translated into long-term clinical practice,” says May.

The current ways of monitoring gut microbiota composition may need some work. There is no individualised and precise way to do it despite next-generation sequencing technologies that can analyse microbial strains, she adds.

“Fecal samples are a non-invasive and inexpensive strategy that can be used to investigate intestinal microbiota. However, we must bear in mind, that the fecal microbiota is just a proxy for intestinal microbiota,” she says.

Managing obesity through gut interventions

  1. Eat a diet rich in fibre to promote the growth of beneficial bacteria
  2. Take probiotics and prebiotics to boost the gut microbiota composition
  3. Follow functional diets such as vegan, gluten-free, and low FODMAP
  4. Get good sleep and exercise regularly to improve the levels of good gut bacteria

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