The gut microbiome contains 100 trillion microbial cells – around the same number as our human cells. These organisms actively interact with our bodies, influencing digestion, immunity, weight, and mental health. A balanced and diverse microbiome is essential for overall health.
The human microbiome is the collection of trillions of microorganisms that inhabit the skin, mouth, gastrointestinal tract and other mucosal surfaces. Ninety percent of the cells within the body are not human cells, they are the microbes and bacteria known as the microbiome.48 The gut itself contains around 100 trillion microbes that are a product of what we inherit from our mothers during birth, what we eat, our environment, and our lifestyle. While studies on the microbiome and its effect on the body are still relatively new, there is significant research that shows that the gut microbiome plays a significant role in body weight regulation. Within the gut, there are “good” bacteria that work with the body to maintain good health, and there are “bad” bacteria that encourage disease in the body, and it requires balance to keep the bad bacteria from overwhelming the good. The microbiome plays an important role in many systems in our body including digestion, hunger and satiety through multiple mechanisms.49 A healthy gut microbiome can have direct metabolic effects on the body, such as enhanced production of hormones that control satiety, increased fat burning and improved insulin sensitivity.52 Therefore, a balanced microbiome is an important ally in healthy weight management.
Three major assaults to the microbiome include unhealthy foods, antibiotics and stress. Not surprisingly, unhealthy, unbalanced eating patterns are harmful to the microbiome. Some bacteria that we get from our diet could indirectly cause weight gain by changing the gut’s behavior. Ultra-processed foods, unhealthy fats, and foods with added sugars, are especially detrimental to the microbiome.
According to the NOVA food classification tool,the extent of food processing is the main driver of the level of quality of the food, with the highest degree of processing categorized as “ultra-processed.” These foods may promote bacterial overgrowth in the small intestine and an unfavorable bacterial overgrowth in the small intestine and an unfavorable microbial composition. Food additives, preservatives and emulsifiers are linked to low-grade inflammation in the gut microbiome.Ultra-processed foods often contain trans fats or hydrogenated fats that can instantly upset the gut microbiome, paving the way to weight gain. Sugar is a favorite food of the harmful bacteria in the microbiome.48 Foods high in sugar don’t always taste sweet and include foods containing refined flour that turns to glucose as soon as it is ingested. Importantly, unhealthy foods will not only lead to an imbalanced microbiome, but in turn, the imbalanced microbiome will lead to powerful cravings for sugar and unhealthy fats, slow down the metabolism and increase the appetite, creating a vicious cycle.48
A balanced microbiome is a healthy one, and diversity of bacterial species is a key component to maintaining this balance. Antibiotics are particularly adept at destroying the critical diversity of the microbiome by acting as a bomb being detonated, destroying both good and bad bacteria alike.
The use of antibiotics is linked to insulin resistance and diet-related obesity. Antibiotics that play havoc with the microbiome include those received via medical treatments, as well as the antibiotics ingested through conventionally farmed animal food products.48,49 While there are ways to reinoculate with healthy bacteria, multiple antibiotic treatments can contribute to a major loss of bacteria in the microbiome that never fully recovers. Therefore, it is critical to use antibiotics only when medically necessary and to eat organic, pasture-raised, grass-fed animal foods whenever possible.
Stress in excess is the culprit in so many diseases, and it is also guilty of creating negative alterations in the microbiome. Unmanaged stress will compromise gut integrity by creating inflammation which is a major factor in obesity, weight gain, and fat retention. The microbiome is so sensitive to stress that even twenty-four hours of high stress levels can significantly change its bacterial population.48 When unhealthy bacteria replace healthy bacteria, the body can go from a fat-burning machine to mainly fat-storing.48 To intensify the effect, an unhealthy microbiome is not just the result of being stressed but can also be the cause of stress, because an imbalanced microbiome can lead to increased anxiety and depression. Therefore, taking steps to mitigate and manage life’s many stressors will support a healthy gut microbiome.
There are several factors that encourage a healthy microbiome, including a healthy diet, probiotics, and prebiotics. If an unhealthy, unbalanced diet is harmful to the microbiome, it is not surprising that a healthy, balanced diet is beneficial. A balanced diet is related to the diversity of the diet. Low microbial diversity is associated with weight gain, with some scientists arguing that the destruction of the microbiome is a prime offender behind the obesity epidemic.48,53,56, 58,59 A healthy diet is one way to increase the diversity of bacteria in the gut. Of particular significance is the consumption of vegetables and fruits, which should be the largest component of a healthy diet.52 There is strong scientific evidence for their ability to prevent numerous chronic diseases. Studies reported that vegetables rich in inulin promoted satiety and reduced body weight. Along with vegetables and fruits, a healthy diet should be complemented by smaller portions of animal-based proteins (fish, lean meat, poultry, eggs and dairy), plant-based proteins (legumes, nuts), and whole grains.52 The term “eating a rainbow” is a good visual for creating a plate filled with colorful vegetables and some fruits, surrounded by the sides of protein and carbohydrates derived from whole food sources.
Probiotics are microscopic organisms that replenish your microbiome by promoting the growth of beneficial bacteria while inhibiting harmful bacteria. They are useful for repair, but their effects are short-lived and depend on continuous consumption. While probiotics do not permanently colonize the gut, they replace beneficial bacteria that has been destroyed and so can help inhibit the overgrowth of destructive bacteria and assist reinoculating the microbiome with good bacteria. Fermented foods contain live bacteria that function as natural probiotics. These foods include sauerkraut, kimchee, fermented vegetables, kefir and some yogurt. There are also several products on the market that can be taken in capsule form. A skilled nutritionist can recommend a reputable brand and may suggest specific strains for particular goals.
Prebiotics are essential for stimulating a healthy microbiome. Whereas probiotics help to replace lost healthy bacteria, prebiotics are the food that feed the existing good bacteria, acting like fertilizer for your healthy microbiome garden 4.8 Inulin is a natural prebiotic found in foods such as garlic, onions, Jerusalem artichokes, jicama, and asparagus. Arabinogalactans are another natural prebiotic found in such foods as carrots, onions, radishes, tomatoes, pears, and kiwi. These are high fiber foods which the bacteria consume. Fiber is critical because, when consumed, the gut breaks it down into short chain fatty acids (SCFAs), including butyrate, which is anti-inflammatory and linked to leanness. The gut bacteria convert the fiber into substances that regulate insulin sensitivity and energy metabolism.49,58,61 This is not an exhaustive list of prebiotic foods. A nutritionist can recommend a full list and create meal plans to include a mix of these natural prebiotics to properly feed the microbiome.
Lastly, exercise and intermittent fasting are also supportive of a thriving microbiome. Regular physical activity has been shown to be an important regulator of a healthy, diverse microbiome, demonstrating that exercise benefits the body in many areas. Intermittent fasting is also supportive because a healthy microbiome is affected not only by what we eat but also by when we eat. Erratic eating patterns such as snacking all day and night eating disrupt the microbiome.62,63 Intermittent fasting enables the digestive tract to rest and digest which gives digestion a break and can help to heal damage to the gut lining. To give your microbiome the most supportive environment, combine healthy eating, natural probiotics and prebiotics with intermittent fasting and exercise.
While there is more research to be done, balancing the bacteria in the microbiome so that the beneficial bacteria are in charge provides a powerful tool for weight loss. An exciting area of research currently being studied is personalized nutrition which uses microbiome sequencing to tailor the nutrition plan to the individual’s microbiome.52 There is still much to learn about the complex interaction of intestinal bacteria with the host. What is clear is that healthy habits create and support a healthy microbiome.
