The gut microbiota and obesity
Obesity is a chronic disease resulting from an excessive increase in body fat, which leads to detrimental health consequences. The development of obesity is determined by a series of interrelated factors, including genetic, endocrine, social, cultural, environmental, and psychological factors; these, in turn, are highly influenced by each individual's energy balance and physical activity. In the long term, obesity is often accompanied by other diseases, such as diabetes, hypertension, cardiovascular diseases like ischemic heart disease and thrombotic disorders, osteoarticular diseases, some types of cancer, gallbladder and liver diseases like gallstones and fatty liver disease, and alterations in fat metabolism. It is also one of the defining elements of metabolic syndrome. These pathologies impair our quality of life. Beyond these, obesity can also lead to psychosocial disturbances such as depression, anxiety, and body image disturbances.
Recent publications suggest that the composition of the gut microbiota may be a significant environmental factor in the development of obesity and its associated metabolic disorders. There is a growing consensus that the gut microbiota can exert a substantial effect on weight management and overall health through its influence on the neuro-immuno-endocrine system. This raises the possibility of considering it as another organ within the body, integrated into its physiology.
The gut microbiota is defined as the collection of living microorganisms that colonize the intestine. The intestinal population comprises trillions of microorganisms belonging primarily to four phyla or types (Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria, with the first two being predominant).
Dysbiosis is a disorder of the gut microbiota characterized by an imbalance in bacterial composition, where harmful bacteria predominate over beneficial ones. The loss of this balance is often associated with diseases such as obesity, diabetes, dyslipidemia, metabolic syndrome, cardiovascular disease, atopic dermatitis (allergies), chronic intestinal inflammation, cancer, and neurological disorders such as schizophrenia and autism, where probiotics appear to be a promising therapeutic option.
Dysbiosis can occur with the indiscriminate use of antibiotics, excessive consumption of processed foods high in fat and low in fiber, exposure to environmental toxins, hepatopancreatic dysfunction, stress, diverticulosis, and can also be influenced by age, intestinal transit time, intestinal pH, and debilitating diseases such as AIDS and cancer. In obesity, a state of dysbiosis occurs, resulting in metabolic alterations that contribute to its development as well as to the development of other associated metabolic pathologies. These alterations include insulin resistance, leptin resistance, elevated short-chain fatty acids, increased growth factors, and the chronicity of the inflammatory response characteristic of obesity due to increased production of cytokines, toxic metabolites, and oxidative stress. These processes, in turn, promote the appearance of cancerous cells. Therefore, alterations in the gut microbiota create an environment conducive to cancer development and can negatively influence its progression and prognosis.
It is well known that a high body mass index (BMI) increases the risk of developing obesity-related diseases and dying from them. Studies have sought a relationship between BMI and the taxonomic composition of the gut microbiota, revealing significant variability and failing to identify a single taxonomic signature in obese patients. This signature refers to how these microorganisms are grouped or organized according to their types or families, and it has not been possible to definitively identify the specific types of bacteria that define the characteristic bacterial community of obese patients. Nevertheless, it is worth considering that modifications in the composition or the presence of certain dominant types of microorganisms in the gut microbiota have metabolic consequences for weight control, and that the use of probiotics could offer a new therapeutic alternative for modifying the composition of microorganisms to be more beneficial. Multiple studies have observed a higher proportion of Firmicutes relatives to Bacteroides relatives in obese patients. Thus, certain interventions (diet, exercise, probiotics) can lead to an increase in the proportion of Bacteroides, thereby achieving a better body weight, a decrease in fat tissue, improvement in metabolic disorders (insulin resistance, leptin resistance), improvement in the chronic inflammatory process characteristic of obesity, modulating the production of pro-inflammatory cytokines, immunoglobulins, and the lymphocyte function of endotoxemia typical of overweight patients, and thus improving their cardio-metabolic profile.
The effectiveness of interventions such as lifestyle modifications for weight loss appears to be influenced by the composition of each individual's gut microbiota, which would explain the variable responses shown by different individuals under similar diet and exercise conditions. Multicenter studies in obese individuals using probiotics, exercise, and diet have shown alterations in the gut microbiota related to weight loss and improvement in BMI. Specifically, Clostridius proportions decreased significantly, with an increase in the proportions of Bacteroides and Prevotella. An increase in the number of Lactobacilli and Bifidobacterium, along with a decrease in Clostridius, has also been observed in obese individuals who experienced significant weight loss.
The use of probiotics has emerged as a promising new alternative in the complementary therapy of obesity, alongside nutritional interventions, physical activity, behavioral therapy, pharmacological therapy, and surgical treatment. Despite these methods, obesity management remains a challenge for medicine. Probiotics may offer benefits when administered because their effects on certain strains could regulate the neuroendocrine and immunological metabolic disorders of the individual and positively affect weight and fat tissue content.
We could conclude that the use of probiotics can be a preventive or therapeutic measure that in the long term can impact the occurrence of chronic non-communicable diseases such as obesity, modulating body weight and decreasing the appearance of comorbidities related to obesity and overweight.
Dr. Lucia M. GonçalvesJardim
Internal Medicine Physician. Specialist in Endocrinology and Metabolism
Literature
- Frias-Toral, Evelyn Paola, and Dolores Rodriguez-Veintimilla. Intestinal Microbiota and Cancer. Journal of Clinical Nutrition and Metabolism 4, no. 1. May 2, 2021. 94-102.
- Álvarez, JM Fernández Real, F. Guarner et al. Intestinal microbiota and health. Gastroenterology and Hepatology. 4, no. 2, February, 2021
- Andreu Prados-Bo, Sonia Gómez-Martínez, Esther Nova, and Ascensión Marcos. The role of probiotics in the management of obesity. Nutr Hosp . 2015;31(Suppl. 1):10-18