Understanding the Link Between Obesity and Type 2 Diabetes
According to the American Diabetes Association (ADA), one of the most notable risk factors for type 2 diabetes is obesity. Obesity raises the risk for type 2 diabetes by increasing the body’s resistance to insulin, the hormone responsible for removing glucose (sugar) from the blood and delivering it to the body’s cells for energy. Additionally, obesity affects the ability of the beta cells in the pancreas to produce insulin.
While it is understood that a combination of genetic and environmental factors contributes to the pathogenesis (development) of type 2 diabetes, the exact mechanisms of the disease remain largely unknown. This ambiguity has led scientists to investigate another potential factor in disease progression – the gut microbiota.
What Is the Gut Microbiota?
The gut microbiota refers to the diverse ecosystem of microorganisms occupying the gastrointestinal (GI) tract. Thousands of years of coevolution have established an elaborate mutual relationship between humans and microorganisms (bacteria, archaea, protists, fungi, and viruses). The presence of microbes has been identified in most locations of the human body, with the GI tract hosting the highest density due to their involvement in digestion.
The Role of Microbes in Digestion and Immune Function
In addition to digestive processes, research has demonstrated that the gut microbiota is crucial to shaping our immune system and carrying out bodily reactions. Thus, there has been an increase in interest in the role of the gut microbiota in disease progression, drug efficacy, and health maintenance.
The Gut Microbiota’s Role in Obesity and Type 2 Diabetes
The ties of the gut microbiota with human metabolism suggest a fundamental relationship with metabolic diseases like diabetes and obesity. Studies have shown that these organisms directly affect inflammation, gut permeability, insulin sensitivity, and glucose/lipid metabolism.
Gut Microbes and Insulin Sensitivity
One of the first clues that suggested the involvement of the gut microbiota in obesity was the observation that germ-free mice (those raised in the absence of microbes) were leaner than conventionalized mice (those with a normal population of microbes). Consequently, when these germ-free mice were introduced to microbes, they demonstrated an increase in fat mass and resistance to insulin.
Microbial Profile Differences in Obesity and Type 2 Diabetes
Furthermore, certain human studies of those with obesity and type 2 diabetes have suggested differences in microbial profiles when compared to individuals without either. However, there is little consistency among studies to identify unanimous changes in individuals with either condition.
Despite conflicting literature, one thing is for certain — changes in microbial profiles are observed in those with obesity and type 2 diabetes. But the question remains- are these microscopic changes driving the disease, or is the disease driving these changes?
How Do Microorganisms Affect My Health?
As living beings, we are constantly performing a series of reactions to maintain balanced health. During these processes, chemicals may be exchanged inside or outside of our bodies. Microbes, as tiny living organisms, are no exception to this concept. Therefore, gut microbes are in constant chemical exchange with their surrounding environment.
Microbial Byproducts and Their Impact on Your Health
Microbial byproducts released into the human environment can influence the processes in our own bodies.
- Inflammation Levels: Microbial byproducts can affect inflammation, which is heavily involved in obesity and diabetes.
- Energy Extraction from Diet: Microbes influence how efficiently calories, and thus energy, are extracted from your diet.
- Fat storage, Glucose (sugar) Metabolism, and Energy Production: Microbes can influence signaling pathways involved in fat storage, glucose (sugar) metabolism, and energy production.
Everyone has a unique population of resident microbes that compose their “typical” gut microbiota. Ideally, this population exists in a balanced manner. However, a drastic disruption of this balance, an event known as dysbiosis, has been attributed to the onset and progression of certain diseases. Some factors known to influence microbial composition are medication (particularly antibiotics), diet, illness, stress, and lifestyle habits (drinking, smoking, exercise, etc.).
Disruption of the Gut Barrier Function
Disruption in the balance of the “typical” microbiota in the gut has a broad range of effects, one of which is decreased gut barrier function. When the intestinal barrier is compromised, contents from the GI system have the potential to enter the bloodstream and travel elsewhere in the body. The circulation of microbial products can lead to certain health conditions. For example, metabolic endotoxemia is a condition that involves low-grade inflammation due to an immune response from the circulation of bacterial lipopolysaccharides (LPS). That said, it is important to recognize that the microbes in our bodies also produce numerous products that positively affect our health.
Fruit and yogurt are a great snack option for promoting a diverse gut microbiota.
Ellie Lane, ©2024, HGIC, Clemson Extension
What Can I Do to Benefit My Gut Health?
In some individuals, prebiotics and probiotics have been shown to improve gut barrier function and inflammation. They have also demonstrated some efficacy in decreasing the accumulation of fat mass and enhancing glucose (sugar) metabolism. Moreover, the gut microbiota is greatly influenced by diet since food also “feeds” your microbes.
Diet and Lifestyle Tips for Gut Health
Because an optimal microbial composition has yet to be identified, experts suggest a diet that promotes a diverse population of microbes. This includes foods that are high in complex carbohydrates (fiber) and plant protein, while generally low in fat. Some examples of beneficial foods are fruit, vegetables, fatty fish, whole grains, and low-fat/fermented dairy products.
Conclusion: The Complex Relationship Between Gut Health, Obesity, and Type 2 Diabetes
Although a correlation between the gut microbiota with obesity and type 2 diabetes has been recognized, there is no substantial evidence to suggest a ‘one size fits all’ framework. While certain approaches have alleviated symptoms for some, this may not be the case for others. The gut microbiota is a complex network that is highly variable within our lifetimes, between individuals, and with extrinsic and intrinsic factors. Despite optimism in the scientific community for the future of microbial research, caution should be taken with therapeutic approaches as the topic remains inconclusive.
Related Resources
HGIC 4395, The Gut Microbiome and Its Role in Health
References
- Arora, A., Behl, T., Sehgal, A., Singh, S., Sharma, N., Bhatia, S., Sobarzo-Sanchez, E., & Bungau, S. (2021). Unravelling the involvement of Gut Microbiota in type 2 diabetes mellitus. Life Sciences, 273. https://doi.org/10.1016/j.lfs.2021.119311
- Gurung, M., Li, Z., You, H., Rodrigues, R., Jump, D. B., Morgun, A., & Shulzhenko, N. (2020). Role of gut microbiota in type 2 diabetes pathophysiology. EBioMedicine, 51. https://doi.org/10.1016/j.ebiom.2019.11.051
- Klein, S., Gastaldelli, A., Yki-Järvinen, H., & Scherer, P. E. (2022). Why does obesity cause diabetes? Cell Metabolism, 34(1), 11–20. https://doi.org/10.1016/j.cmet.2021.12.012
- Li, W.-Z., Stirling, K., Yang, J.-J., & Zhang, L. (2020). Gut microbiota and diabetes: From correlation to causality and mechanism. World Journal of Diabetes, 11(7), 293–308. https://doi.org/10.4239/wjd.v11.i7.293
- Sharma, S., & Tripathi, P. (2019). Gut microbiome and type 2 diabetes: Where we are and where to go? The Journal of Nutritional Biochemistry, 63, 101–108. https://doi.org/10.1016/j.jnutbio.2018.10.003
