Gut Microbiota: What’s the Hype?
Most people know that obesity and obesity-related diseases, such as diabetes, are mainly caused when we eat high-fat or high-calorie foods. Although eating more calories than the body can burn results in the accumulation of fat within the body, scientists believe that other mechanisms may be involved—they suspect that the composition and diversity of organisms living in our gut, also called microbiota, may indirectly be associated with the development of obesity and other metabolic disorders.
In the past few years, several studies have been conducted to understand which microbes, or microbial drugs, are the best targets to improve health, facilitate weight loss, or prevent obesity. While there are conflicting findings from studies that have failed to show that gut microbiota has a tremendous role in the way our bodies function, there is accumulating evidence that these microorganisms indeed play a role in regulating energy balance and weight and other metabolic disorders such as diabetes. Below is a summary of the methods and main findings of some interesting researches on microbiota:
Bäckhed and colleagues showed that when gut microbes from conventionally raised mice were transferred to germ-free mice, the later gained weight (60% increase in body fat) and developed insulin resistance within 2 weeks despite increased activity and decreased carbohydrate consumption. Simply put, the gut microbiota affects energy harvest from the diet and energy storage in the host.
Some researchers fed three groups of mice (germ-free mice, conventionally raised mice, and mice that were exposed to high doses of antibiotics) with a calorie-rich diet. Conventionally-raised mice developed obesity and insulin resistance, while the other two groups remained lean and had better insulin sensitivity (i.e., body cells respond better to insulin, which helps regulate the amount of sugar in the blood).
So how are these findings relevant to human health?
When microbiota from normal mice are administered to germ-free mice are, some proteins that regulate fat metabolism are suppressed, resulting in the deposition of fat in adipose tissues. These proteins (called fasting-induced adipose factor or Fiaf) have been suggested to play an important role in regulating fat metabolism in humans. However, it is unclear how microbiota contribute to obesity and diabetes in humans and scientists are still faced with multiple challenges, including the fact that many factors are associated with obesity and diabetes.
Scientists believe that the manipulation of the gut microbiota represents a new perspective to treating obesity; however, it cannot be considered a substitute for diet and exercise.