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Dietary interventions in obesity linked to changes in gut bacteria

Dietary interventions in obesity linked to changes in gut bacteria

At Deakin’s Food & Mood Centre, Professor Felice Jacka and her team are working in the exciting new field of nutritional psychiatry, aiming to understand the complex ways in which the food we eat influences our brain, mood, and our physical and mental health.


One important focus of their research is the gut microbiota: the bacteria that live within the gastrointestinal system.

Did you know that we have more bugs in our gut than we have human cells in our bodies? Our gut bacteria play a vital role in metabolism and the function of our immune system.

Having a diverse and abundant mix of “good” gut bacteria is linked to better health outcomes, with evidence that it reduces the risk of developing conditions such as obesity, diabetes, heart disease, and some autoimmune diseases and mental health disorders.

The foods we eat significantly impact the composition and diversity of our gut bacteria.

“In general, eating a diet rich in plant-based whole foods – vegetables, fruit, wholegrains, legumes, nuts and seeds – promotes a greater variety of gut bugs and may help to reduce inflammation in the body,” Melissa Lane, a PhD candidate at the Food & Mood Centre, explained.

The fruit and vegetable section at the supermarket.

“But starving our gut bacteria of fibre can lead them to eat the only food in sight – the mucus lining that protects our gut wall. This may activate the immune system and provoke an inflammatory response.”

“The idea that we can modify our gut bacteria through changes to our diets is an empowering one,” Melissa said.

And the response can be really fast: “Research shows that we can change the composition of our gut bacteria, for better or worse, within a matter of days.”

But the beneficial changes to the gut microbiota associated with eating a fibre-rich diet only last for as long as you continue to consume a variety of high-fibre foods each day.

In February 2020, the Food & Mood Centre will begin a new research trial called the MicroFit Study, which looks at changes to the gut microbiota following very-low calorie diets (< 900 kcal per day) in women with obesity.

“Obesity is a serious metabolic disorder linked to increased risk of a whole range of conditions and diseases such as heart disease, stroke, diabetes, mood disorders and some cancers,” said Melissa.

The rate of obesity in Australia has doubled in the past decade, with almost a third of Australians now classified as obese. That’s 5.8 million Australians living with obesity, which is costing the country almost $12 billion a year.

Research is showing that our gut microbiota has a powerful affect on our metabolism – how we absorb, metabolise and store calories. Reduced diversity of the gut microbiota is associated with the development of obesity.

But it has been shown that obese individuals can change their gut bacteria through dietary changes and weight loss. Lifestyle modifications, such as healthier eating and increased physical activity, are the first-line strategy for obesity intervention.

A close up of a person's legs while running.

However, when these changes prove inadequate, the National Health and Medical Research Council of Australia recommends other options, including very-low calorie diets that have been carefully formulated to provide sufficient levels of nutrients.

Melissa explained that the MicroFit Study will build on research suggesting very-low calorie diets and weight loss in individuals with obesity are linked to changes in the gut microbiota composition.

The trial will also assess whether these changes impact metabolic and mental health outcomes.

“The study aims to understand the impact of different dietary strategies, in the context of very-low calorie diets, on the gut microbiota and associated health outcomes in obesity.”

With obesity at epidemic proportions, this research will help delineate exciting new treatment options for this debilitating chronic medical condition.


To support the Food & Mood Centre’s cutting edge research to find solutions to leading causes of disability and suffering, visit deakin.edu.au/giving.

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