As warmer weather creeps up on us, the rising temperature brings with it a renewed determination to finally tackle those weight loss goals. You remember them, right? The ones so optimistically laid out in January? But while focus may be collectively turning toward that extra bit of gut around the waistline, most people probably aren’t thinking too much about what’s hanging out inside their guts (and I don’t mean that chocolate chip scone from this morning). I’m talking gut bacteria here.
Several recent studies have shown that certain gut bacterial species change with varying amounts of body fat. What's more, gut bacteria transferred from obese mice to thin mice cause rapid weight gain in the recipient. According to a new study published in the March 27th issue of Science Translational Medicine, the makeup of a person’s gut bacteria population following gastric bypass surgery plays an important role in the resulting weight loss.
On average, a person's intestines play host to around 100 trillion bacterial organisms representing around 500 different microbial species. These varied bacteria are all competing to dominate the gut population, but some are more beneficial to the host than others. The microbes that foster a mutualistic relationship can do a variety of useful functions for us including producing vitamins and nutrients, synthesizing hormones and regulating metabolism. On the other hand, an over proliferation of the wrong kind of gut flora may contribute to irritable bowel syndrome, infections and even cancer. The key to keeping everything healthy and happy, it seems, is to get the balance of bacterial numbers just right.
In the recent study linking gut flora and health, collaborating groups from Harvard’s Systems Biology department and Massachusetts General Hospital discovered that the right makeup of gut bacteria can bring about weight loss. It was first noted that patients who had undergone gastric bypass surgery had a significantly changed gut bacterial population afterwards. Interestingly, it is thought that the primary reason people lose 65 – 75 percent of their excess weight following bypass surgery is due to an increase in metabolism rather than a smaller stomach size.
Researchers investigated these findings further by performing gastric bypass surgeries on obese mice and assaying the resultant microbial populations. At the same time, another group of obese mice were simply cut open and sewn shut to mimic the act of surgery in a (dubiously named) “sham” operation. The mice that had the bypass surgery lost about 30 percent of their weight and were found to have significant changes in their gut flora compared to the "sham” operation group. Even when the "sham" group was put on a diet and made to lose weight, their bacterial population remained mostly unchanged. This indicated that something about the gastric bypass surgery altered the gut ecosystem allowing a different, weight-loss triggering population of bacteria to thrive.
The next step was to take the bacterial populations from the intestines of mice that had undergone bypass surgery and transfer them to sterile obese mice whose own gut bacteria had been eradicated. Surprisingly, the recipient mice rapidly lost 5 percent of their weight. While four subtypes of bacteria were pin pointed as having changed the most after the surgery, the researchers could not say for sure what mechanism linked the microbes to weight loss but speculated that it was due to an overall increase in metabolism. Ultimately, with further research the goal would be to see if microbial population transfers between humans have the same effect. If successful, transplantation or tweaking of gut bacteria would present an attractive option for weight loss patients who want to avoid surgery.
Gut bacteria have been fairly popular in the news lately with research revealing that maintenance of gut microbiota is connected to better health and longer lives. Repopulation of gut bacteria using “synthetic poop” has been proposed as an attractive new therapy for patients suffering from resistant C. deficille infections. Now you can even find out what’s in your own gut; and if you don’t like it, options in the future may let you swap it out for a healthier tailor-made population. In the meantime, for those carrying around a little extra weight, it might be comforting (or not) to know that a good 3 pounds of that weight can be attributed to the mass of bacterial cells living inside you. Which is pretty neat, right? No, who I am I kidding? That fact is just gross.
Photo: Trillions of microbes populate our guts including Escherichia coli, pictured here.