Important Points:
- Microbiome
- Bacteria
- Storage
What is the human gut microbiome?
The human microbiome is the community of bacteria living in your gut, and they outnumber your own cells. They digest fiber you cannot, they decide how much of a meal becomes stored energy, and the mix in an obese gut is different from the mix in a lean one.
We traditionally think of bacteria as dirty, something we want to keep outside of our bodies. Intestinal bacteria are very important for digestion; they break complex fiber polysaccharides (sugar molecules connected to each other) into simple absorbable sugars by a process called fermentation, converting nutrients into calories. The large intestine alone houses over 1400 species of bacteria numbering over 100 trillion. In reality, the human body contains ten times more microbial cells than human cells, and the human body is dependent upon the genetic information encoded in these bacterial cells for specific metabolic pathways.
Our microbial partners have co-evolved with us, in a beneficial (symbiotic) relationship involving nutrient sharing. The ability to store energy would be a beneficial attribute for ancient humans as they had variable access to food. When nutrient dense food supply was available, their consumption and storage would benefit both them and their bacterial symbiotes later when food supplies were diminished. However, in modern, developed societies where there is ready access to large-portion, high-calorie diets, this “benefit” becomes a detriment, and we develop a previously rare condition called over-nutrition, over-storage, or obesity.
Obese individuals have a different mix of bacteria in their guts than thin people. The ratio of Firmicutes to Bacteroidetes (called the F/B ratio) is higher in obese people than in lean people, and it drops as those people lose weight. Both Firmicutes and Bacteroidetes bacteria are involved in complex polysaccharide breakdown, but Firmicutes are much more efficient than Bacteroidetes bacteria; therefore, having more Firmicutes bacteria in our gut makes more energy available leading to increased caloric intake and eventually obesity. Firmicutes overload is also associated with slowed intestinal motility, commonly known as chronic constipation.
In studies of genetically identical twins, bacterial populations have been found to differ, depending on whether the twin is lean or obese, with much higher level of Firmicutes in the obese twins. In obese patients undergoing gastric bypass surgery, colonic bacteria change to become more like those of normal-weight individuals after the operation, reducing their Firmicutes levels.
Antibiotic overutilization may also indiscriminately eradicate the beneficial bacteria in your gut along with the bad ones. Conventional farmed meats are doped with antibiotics, with nearly 50-70% of all antibiotics produced in the United States used on healthy livestock to promote growth and weight gain in the animal feed. Consuming these antibiotic-laden meats may be a significant factor enhancing growth and weight in the human population [obesity] as well. Eating grass-fed and organically raised meats of all kinds can reduce this antibiotic intake.
The amazing thing to keep in mind is that you can rapidly – within 72 hours – change your gut bacteria to a healthy ratio simply by immediately eliminating refined carbohydrates and increasing your fiber intake. Supplements of “get thin bacteria” will soon be available as well.
Frequently asked questions
How can I improve my gut microbiome?
Cut refined carbohydrates right away and eat more fiber. Those two changes can shift your gut bacteria toward a healthier ratio within 72 hours. Choosing grass-fed and organically raised meats also lowers the antibiotics you take in from conventionally farmed meat, which helps protect the beneficial bacteria you already have.
What ruins your gut microbiome?
Antibiotics are a major culprit. Overusing them can wipe out the beneficial bacteria in your gut along with the harmful ones. You also take in antibiotics indirectly: 50 to 70 percent of the antibiotics produced in the United States go to healthy livestock to speed growth and weight gain, and eating that meat may drive weight gain in people as well.
Can gut bacteria cause weight gain?
They can tip the balance. Obese people carry a higher ratio of Firmicutes to Bacteroidetes bacteria than lean people. Firmicutes pull more energy out of the fiber you eat, so more of each meal becomes available to store. In identical twins, the obese twin carries far more Firmicutes, and the ratio falls as people lose weight.
How many bacteria live in your gut?
More than 100 trillion, spread across over 1,400 species in the large intestine alone. The human body holds about ten times more microbial cells than human cells. You depend on the genes in those bacteria for specific metabolic pathways, including breaking complex fiber down into simple sugars you can absorb, a process called fermentation.
