Have you ever heard the phrase that our gut is our second brain? Well, this couldn’t be more true.  

The Gut Microbiome: The Basics

The gut microbiome is a community of microorganisms, including bacteria, fungi, and viruses. It serves a bigger purpose than just aiding digestion. These tiny inhabitants have an impact on various aspects of our well-being, such as mood, immune response, weight regulation, and nutrient absorption.

What is the Gut-Brain Axis?

The relationship between our central nervous system (brain and spinal cord) and enteric nervous system (our digestive system), is known as the “gut-brain axis1.” It’s a system that showcases how closely linked our digestive system is with our brain.

The enteric nervous system, often referred to as our “second brain,” sends various messages through hormones and neurotransmitters, informing our brain about sensations such as hunger, satiety, and the timing of gastric emptying. In the same way, our brain reciprocates by influencing gut activity. These two systems work together, communicating and influencing each other in a number of ways.

The Role of Our Gut’s Brain

Our gut certainly has a brain of its own. Our gut is comprised of over 100 million nerve cells lining the entire gastrointestinal tract. The enteric nervous system plays a major role in governing the digestive process, from the swallowing of food to the release of enzymes that break down nutrients. But, its influence extends beyond just digestion. The ENS communicates directly with our central nervous system by relaying vital information about our internal environment and influencing mood, immunity, and even cognitive function. 


You might already be aware that certain neurotransmitters like serotonin and dopamine are prevalent in our brain, but what you may not know is that these same neurotransmitters are also produced in the gut. In fact, 95% of the body’s supply of serotonin2 is synthesized by gut bacteria! Serotonin promotes happiness and a sense of ease while dopamine brings pleasure and satisfaction.

When we experience feelings like anxiety and stress, it can directly impact our gut. For instance, heightened stress levels can lead to gastrointestinal issues, slow down digestion, or even exacerbate conditions like irritable bowel syndrome. In the same way, if we have an unbalanced microbiome, it can actually lead to feelings of depression and other mental conditions. This is because if the gut isn’t able to properly produce the necessary amounts of these neurotransmitters, mental health can be impacted.

Researchers are now finding that individuals who struggle with anxiety, depression, and other psychiatric conditions often end up leading to the development of GI conditions, such as Irritable Bowel Syndrome or Peptic Ulcers4. This leads us to believe that the mechanism between the gut and the brain works in both directions. This finding has been profound as it provides hope that altering the gut microbiome might play a role in minimizing chronic diseases and psychiatric conditions.


There is an array of hormones that our body produces that influence our sensations of hunger and fullness. Ghrelin, often dubbed the “hunger hormone,” signals our brain to eat, while leptin, the “satiety hormone,” tells our brain when we are full.

Intriguingly, the balance and functioning of these hormones can be influenced by the bacteria in our gut microbiome. Certain gut bacteria can affect the production and responsiveness of ghrelin, leptin, and other hormones, potentially leading to heightened cravings or prolonged feelings of hunger. An imbalanced or unhealthy microbiome might disrupt this delicate hormonal balance, pushing individuals towards overeating or opting for less nutritious food preferences. 

Supporting this theory, studies3 have identified marked differences in the gut microbiomes of obese versus lean individuals, suggesting that the presence or absence of specific bacterial strains can have a profound impact on weight management through their effect on these hunger-regulating hormones.


Of course, our gut’s brain is also responsible for pursuing optimal digestion. The health and balance of our gut are intrinsically tied to the efficiency of our digestive process. 

For starters, a balanced gut flora aids in the breakdown of complex food substances. Some bacteria, for instance, are adept at fermenting dietary fibers, which can then produce short-chain fatty acids. These not only serve as a source of energy but also support the health of our gut lining, ensuring optimal nutrient absorption. When the gut flora is imbalanced, nutrient absorption can become compromised, potentially leading to deficiencies even if our dietary intake is adequate.

Factors Affecting the Gut Microbiome and Weight

A healthy gut is a happy gut. In order to effectively manage weight or whatever your health goal might be – it all comes down to the gut. The composition of our gut microbiome is linked to various lifestyle and environmental factors, which in turn play a significant role in determining our ability to manage weight.


Diet, undeniably, has a profound influence on our gut and weight. Consuming probiotics, which are live beneficial bacteria, can help promote a healthy gut flora and help to restore any imbalances. Additionally, consuming prebiotic fiber helps the probiotics to thrive and flourish. Some natural sources of probiotics are typically fermented foods like yogurt, sauerkraut, and kimchi.  These natural probiotic-rich foods introduce diverse and beneficial microorganisms that can enhance gut diversity and health.


Beyond diet, our daily routines and habits also exert an impact on the way our gut functions. Chronic stress, inadequate sleep, and lack of physical activity can disrupt the balance of the gut microbiome, often leading to issues that indirectly affect weight, such as impaired digestion or heightened inflammation.


Antibiotics wield a particularly strong influence on our gut microbiome. Of course, antibiotics are necessary in treating bacterial infections, but they can significantly reduce microbial diversity in the gut. This is because antibiotics are meant to destroy all bacteria in the body, but unfortunately, they can’t distinguish between the good and bad species, resulting in all of them being wiped out. So, if you find yourself needing to take an antibiotic, it may be helpful to take a probiotic supplement simultaneously.

Promoting a Healthy Gut for Weight Management

It’s clear that the status of our gut makes a huge impact on the rest of our bodily systems. From digestion to appetite regulation and mood, the health of our gut can influence all of these processes. 

It’s much more attainable to manage weight when our digestion is enhanced, our appetite is under control, and our mood is stable.

Consuming probiotic-rich foods or probiotic supplements is a great way to help replenish the microorganisms in your gut. Additionally, consuming prebiotic fibers like oats, seaweed, bran, and artichokes will provide the probiotics with the fuel source they need to thrive.

Managing stress and ensuring adequate sleep are just as important as diet. When stress levels remain high, it can negatively influence the microorganisms in the gut and disregulate the hormones and neurotransmitters needed for optimal digestion. Finding ways to help manage your stress, whether it be yoga, meditation, or deep breathing, is critical for any healthy lifestyle. Lastly, maintaining proper sleep hygiene by refraining from blue light an hour before bed and establishing a consistent sleep-wake routine can promote deeper, restorative rest.

  1. Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology, 28(2), 203–209
  2. Carpenter, S. (2012). That gut feeling. https://www.apa.org. https://www.apa.org/monitor/2012/09/gut-feeling
  3. Davis, C. D. (2016). The gut microbiome and its role in obesity. Nutrition Today, 51(4), 167–174. https://doi.org/10.1097/nt.0000000000000167
  4. Sarkhel, S., Sarkar, R., & Dhali, G. K. (2017). Anxiety and Depression in Irritable Bowel Syndrome. Indian journal of psychological medicine39(6), 741–745. https://doi.org/10.4103/IJPSYM.IJPSYM_46_17