Obesity is a global phenomenon of epidemic proportions. According to the latest statistics from the World Health Organization (WHO), 13% of adults worldwide are already obese. In the United States, the proportion has risen to more than 40%.
Obesity is associated with a raft of physical ailments, including diabetes, heart disease, and certain types of cancer. There are also possible mental health effects relating to loss of mobility and, in some cases, social isolation and a reduced ability to work.
Bacteria are important to a variety of basic body functions, including metabolism control. Bacteria in the gut produce metabolites, some of which play a role in breaking down food, potentially helping control body weight.
Research has shown that people with obesity have a smaller number of bacteria in their intestines. Consequently, the microbiota tends to be a factor in deciding who does and does not have obesity.
Choosing Gastric Bypass Surgery
Surgical options are available for people who are unable to lose weight on their own by diet and exercise and whose health is at risk due to their weight.
Another of these steps, gastric bypass surgery (also known as Roux-en-Y surgery), also changes the composition of bacteria in the intestine.
With this knowledge in hand, the researchers behind the new study investigated how and when the microbiome changes after gastric bypass surgery, and what this means for how people break down the foods that they consume.
The researchers characterized the microbial communities in nine people with severe obesity before their gastric bypass surgery, as well as 6 months and a year after the procedure.
In addition to comparing the microbial communities across these time points, the researchers also compared them with the communities present in 10 control subjects and a cohort of 24 people who had undergone surgery 13–60 months previously.
The findings appear in the Nature journal Biofilms and Microbiomes.
Microbes and metabolism As predicted, all participants lost weight after surgery. However, researchers have observed differences in their microbiomes, which were tested in two locations: the rectal mucosa (the rectum liner) and the feces.
Most previous studies have largely relied on the latter because sampling mucosal surfaces is much more challenging and invasive. This research is therefore an important move forward.
“The mucous membrane is a critically important site for host-microbe interactions. We understood that with fecal sampling, we had an underrepresented picture of how the mucosal communities actively interact with host immune system and epithelial cells,” explains lead author Zehra Esra Ilhan, Ph.D.
Researchers have reported major improvements in both cultures. Changes to the fecal microbiota were more dramatic, occurred within 6 months of surgery and continued for a longer period of time.
Microbiome modifications were also correlated with altered food fermentation, including shifts in the breakdown of fats and bile acids — both of which are correlated with enhanced metabolism.
“Our findings illustrate the importance of changes in the mucosal and fecal microbiomes that are expressed in the metabolism of the intestines after surgery,” says Ilhan.
Could a probiotic supplement surgery?
This research sheds new light on the mechanisms by which gastric bypass surgery can induce weight loss, gastric restriction and feeling full soon after feeding.
This may also lead to alternatives to a treatment that is invasive, costly and not always effective in the long term.
Many people regain the weight they lose following surgery, which the authors of the study say may be because their microbiome is not conducive to permanent weight loss. They find that some people can “lack the desirable microbes required for permanent weight loss.”
“Understanding the microbial behavior in the gut could potentially lead to creating a probiotic that could replace surgery — or an improved indicator to identify the best candidates for surgery and sustained weight loss.” –co-author Prof. Rosa Krajmalnik-Brown
While this is a very exciting prospect, it is important to note that a small sample size was used in this analysis.
More detailed studies are needed to validate the results of this research and further test the hypothesis that the microbiome promotes weight loss.