From Science Daily with Dr. Mercola
A single molecule in your intestinal wall, activated by the waste products from gut bacteria, plays a large role in controlling whether you are lean or fatty. When activated, the molecule slows the movement of food through the intestine, allowing you to absorb more nutrients and thus gain weight.
Bacterial byproducts are a source of nutrients, but now it appears that they can also be chemical signals used to regulate body functions.
Humans have a large and varied population of beneficial bacteria that live in their intestines. The bacteria break up large molecules that the host cannot digest, and the host in turn absorbs many of the resulting small molecules for energy and nutrients.
Researchers focused on two species of bacteria that break up dietary fibers from food into small molecules called short-chain fatty acids. They found that short-chain fatty acids can bind to and activate a receptor molecule in the gut wall called Gpr41.
When researchers disrupted communication between the bacteria and the receptor in mice, they found that their intestines passed food more quickly, and the mice weighed less and had a leaner build, even though they ate no less than other mice.
Science Daily October 19, 2008
Proceedings of the National Academy of Sciences October 17, 2008 [Epub ahead of print] (Free Full-Text Article)
Dr. Mercola's Comments:
These findings highlight the symbiotic relationship you maintain with the tens of trillions of microorganisms that populate your intestine. The bacteria in your gut actually outnumber the cells in your body by 10:1. Unfortunately, the overuse of antibiotics, antibacterial agents, and even the ever increasing practice of sterilizing food through radiation and pasteurization may have far more wide ranging health effects than anyone can imagine.
Although I don't believe these findings are the explanation for the obesity epidemic, I believe it may be a factor. After all, inside your gut is a living ecosystem, full of both good bacteria (probiotics) and bad bacteria that play a major role in your physical and even mental health. So it's not a big stretch of the imagination to think that some change, like food additives or antibiotic use, might have caused a fundamental, widespread shift in gut flora, making it easier for many people to gain weight, and increasingly difficult to shed extra pounds.
Obesity has been named the fastest growing health threat in the United States, where two-thirds of adults are already overweight or obese. Among some groups the rates are even higher, such as African-American women, of whom 78 percent are currently overweight or obese.
Is Your Gut Bacteria Making You Fat?
This is not the first time gut bacteria has been implicated as a cause of obesity. Multiple studies have shown that obese people have different intestinal bacteria than slim people.
The functioning of this gut microflora in your body can be likened to that of an ant farm, working together as an intelligent whole to perform an array of functions, which include extracting calories from the foods you eat.
Hence, the microflora in your gut could play a key role in obesity, as it appears that the microbes flourishing in an overweight body are much more efficient at extracting calories from food.
Two studies supporting this theory - one looking at mice, the other using humans - found that a family of bacteria known as firmicutes was more plentiful in the obese (20 percent more), whereas another bacteria called bacteroidetes was almost 90 percent lower in obese subjects.
Firmicutes appear to be more efficient at taking calories out of complex sugars and depositing those calories in fat. When these microbes were transplanted into normal-weight mice, they suddenly gained twice as much fat.
In the human study, obese people who lost weight increased their bacteroidetes, while the numbers of firmicutes decreased.
Another study published earlier this year in the American Journal of Clinical Nutrition also concluded that the types of bacteria in a child's gut may influence his or her risk of becoming overweight or obese.
They discovered that children with high numbers of bifidobacteria and low numbers of Staphylococcus aureus (an antibiotic-resistant strain of bacteria) appeared to be protected from excess weight gain. On average, the bifidobacteria counts were twice as high in healthy weight children as in those who became overweight by the age of seven, while staphylococcus levels were lower.
The researchers suggested that staphylococcus aureus may cause low-grade inflammation in your body, which could contribute to obesity.
Further, their findings might help explain why breast-fed babies run a lower risk of becoming obese, as bifidobacteria predominate over potentially harmful bacteria in the guts of breast-fed babies.
Have You Heard of Infectobesity?
Taking the gut bacteria/obesity connection one step further is the relatively new term "infectobesity," which suggests that obesity may be caused by a virus or other disease-causing organism.
For instance, the human adenovirus-36 (Ad-36) -- a cause of respiratory infections and pinkeye -- may also be a contributing factor to obesity, as it's been found to transform adult stem cells into fat cells that are capable of storing additional fat.
"Infectobesity" is also a plausible theory. It is certainly possible that viruses could be a contributing factor in many cases of excessive weight gain.
However, please don't take this to mean that losing weight is out of your control, or something that can only be done using an anti-viral medication.
This theory actually further supports the importance of balancing out the bacteria in your gut, because the foods you eat and the integrity of your immune system are two important factors that determine whether you'll be able to successfully fight off a viral infection.
Experts believe about 70 percent of your immune system is located in or around your digestive system. And if your digestive system is crawling with unhealthy bacteria, there's a good chance that your immune system will be suppressed as a result.
So it seems all roads lead back to this one central premise: optimizing your gut bacteria is essential for your good health, which includes maintaining a healthy weight.
How to Optimize Your Gut Flora
The good news is that positively influencing the bacteria growing in your body is relatively easy.
One of the most important steps you can take is to stop consuming sugary foods. Eating a healthy diet low in sugars, grains and processed foods will generally cause the good bacteria in your gut to flourish, and naturally build up a major defense against excessive amounts of bad bacteria that can damage your health.
This is one of the many reasons I highly recommend reducing, with the plan of eliminating, sugars and most grains from your diet. Eating foods that are suitable for your nutritional type is also an important aspect of shedding excess pounds, as you will then give your body the fuel it needs to run optimally.
But even with an extremely low-sugar diet there are other factors that negatively influence your gut bacteria, including:
- Chlorinated water
- Antibacterial soap
- Agricultural chemicals
All of these things help to kill off your good bacteria. This is why it's a wise choice to "reseed" your body with good bacteria from time to time by taking a high-quality probiotic supplement or eating properly fermented foods like natto.
Keep in mind, of course, that if you or your children need to lose some excess weight, balancing your gut bacteria is only one part of the equation. Regular exercise and addressing any emotional blocks are also very important.