From gut to mind: Exploring prebiotics and probiotics as dual fighters against depression and obesity

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Depression is among the most prevalent and potentially serious mental health disorders, accounting for up to 800,000 suicides a year. The risk factors for depression have, therefore, undergone much exploration.

A recent study published online in Nutrients deals with the interactions between depression and nutrition, coupled with exercise.

Study: The Role of Gut Microbiota, Nutrition, and Physical Activity in Depression and Obesity—Interdependent Mechanisms/Co-Occurrence. Image Credit: Bits And Splits/Shutterstock.comStudy: The Role of Gut Microbiota, Nutrition, and Physical Activity in Depression and Obesity—Interdependent Mechanisms/Co-Occurrence. Image Credit: Bits And Splits/

About depression

Depressive disorders include several categories, including persistent depressive disorder (dysthymia), premenstrual dysphoric disorder, as well as depression induced by addictive drugs or medications or by medical conditions.

All are characterized by sadness and irritability, with bodily and mental changes. The effect is a lowered quality of life and impaired functioning.

Moreover, depression is known to increase the risk for a number of metabolic diseases, such as diabetes, obesity, and ischemic heart disease.

Conversely, dietary patterns are linked to mental health as well as malnutrition. For instance, excessive fat intake leads to chronic inflammation and obesity.


Obesity is defined as the accumulation of body fat in excess, as measured by the body mass index (BMI) and the body fat percentage. It is associated with a higher risk of cardiovascular disease (CVD), insulin resistance, cancer, and nerve damage.

Risk factors for obesity are well-known and include gender, age, smoking, apart from the consumption of excessive fat and of processed foods, which are typical of Western diets.

Obesity and depression often affect the same individual, along with anxiety disorders. They have a common mechanism of action, as seen by their bidirectional association.

People who are depressed often indulge in comfort eating, which may increase body weight, especially if the person is also inactive. The risk of obesity in people undergoing emotional stress is almost 40% higher.

Similarly, obese people are almost 20% more likely to become anxious or depressed because of negative self-image as well as adverse social perceptions that they are too lazy or undisciplined to regulate their diet and their weight. The treatment of depression with antidepressants is effective but may cause weight increase.

Unfortunately, both obesity and depression are among the most prevalent disorders globally and have a high death rate, leading to powerful scientific interest in their interrelationships.

Gut microbiota

The gut microbiota is essential to proper energy storage and metabolism, but shows marked variability in obese vs lean individuals. This includes lower diversity and fewer commensal bacteria but more pathogenic microbes in the obese. The resulting aberration in metabolism may contribute to obesity.

The need for a rational diet along with therapies like psychotherapy and medication to treat patients with depression is stressed by some scientists.

In addition, probiotics and prebiotics may be required, along with nutritional supplements, to correct dysbiosis and vitamin deficiencies.

Probiotics and gut microbiota

The researchers sought to understand how gut microbes may be useful in treating both obesity and depression and the role of probiotics and prebiotics in such therapy.

The review suggests that about 57% of the composition of the gut microbiota responds to dietary patterns.

Probiotics strengthen the gut barrier and modulate the immune system. Their use is associated with improving depressive symptoms, perhaps by supplying vitamin D and short-chain fatty acids (SCFAs), which combat inflammation.

Some strains of probiotic bacteria directly affect neural pathways. They inhibit the depression-inducing hypothalamic–pituitary–adrenal axis (HPA axis), and promote the secretion of the anti-stress neurotransmitter GABA, also known as gamma-aminobutyric acid.

Others produce gut neurotransmitters that also affect the brain, affecting the mood for the better.

Some clinical trials in humans suggest a positive effect of probiotics on depressive disorders as well as on obesity and related metabolic conditions like insulin resistance, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).

Further research is essential to validate these results, especially as probiotics work well on gut health and overall disease control only as part of a holistic management strategy, including proper diet, exercise, stress regulation, and adequate sleep.

Bacterial strains linked to improved neural pathways, sometimes called psychobiotics, include multiple Lactobacillus strains like Lactobacillus casei Shirota, Lactobacillus fermentum NS8 and NS9, and Lactobacillus rhamnosus JB-1, as well as Bifidobacterium strains like Bifidobacterium longum Rosell-175, Bifidobacterium longum 1714, and Bifidobacterium longum NCC3001.

Diet and mental health

The brain receives a good share of absorbed nutrients and utilizes them to keep itself healthy. For instance, regeneration, neuroplasticity, and an adequate antioxidant reserve depend on the proper supply of nutrients to the brain.

Supplementation with fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), magnesium, folate, and vitamins E and D have been suggested to be beneficial in countering or mitigating severe depression and reducing neuroinflammation.

Specific diets like the Mediterranean diet (MD), the DASH (Dietary Approaches to Stop Hypertension), or vegetarian diets have frequently been assessed for their relationship with physical and mental health.

The authors of the current study found reduced depression and obesity risk with both the DASH and the MD, but contradictory data with vegetarian and vegan diets. However, high-quality vegetarian diets were protective against depression, underlining the pivotal role of diet quality in the type of diet chosen.

Physical activity and obesity/mood disorders

There is ample evidence that weight management is aided by increasing the overall energy expenditure and improving the mood, with reduced anxiety and depression. Aerobic exercise has been recommended for its ability to build fitness and help reduce weight.

Physical exercise is linked with lengthening telomeres, a metabolic health biomarker. It is also associated with better brain health, sleep quality, and reduced depressive symptoms.

Physical exercise is also linked to better gut microbiota composition, stronger commensals, and more anti-inflammatory bacteria.

Early-life exercise may promote the development of bacteria that can help the host adapt to changing conditions and promote healthy brain development.

The broader impact of obesity and depression

Depression is associated with increased mortality and morbidity, absenteeism, severe decreases in the quality of life, and reduced productivity.

Obesity, which is currently estimated to have a prevalence of 30% in the USA, also has profound impacts on personal and social health. It reduces female fertility, promotes loss of cognitive ability, reduces the lifespan, and may increase employment difficulty.


Obesity and depression have common origins and act to exacerbate each other. This interrelationship significantly impacts the quality of life. One possible explanation for their connections may be via gut dysbiosis.

This has stimulated much study on the potential use of probiotics and prebiotics in depression and anxiety, as well as in obesity.

Encouraging findings from existing research underscore the need for robust clinical trials to evaluate the therapeutic potential of microbiota modulation.”

Journal reference:
Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.


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