Are gut bacteria and weight loss linked?

You probably know that your body is home to trillions of bacteria that mostly reside in the gut, which is referred to as the gut microbiome. What’s really interesting about this, though? These tiny microorganisms may drastically affect our health, both negatively and positively; however, we don’t really know much about them.

So many mysteries remain regarding our microbiomes but research indicates the bacteria in our guts might modulate our weight and play a major role in our risk of developing obesity, diabetes, and more.

In addition, our gut microbiome may influence how our bodies respond to specific foods. Researchers from the Weizmann Institute of Science recently observed the blood-glucose levels of 800 patients after consuming various foods, which found a diverse range of outcomes varying significantly between participants.

Obviously, some participants experienced an increase in blood sugar after eating desserts high in sugar like ice cream or chocolate. However, other participants experienced the same increase after eating bananas or tomatoes. Interestingly enough, a significant amount of participant’s glucose levels increased after eating brown rice.

Modern-day dieting, which relies on general recommendations that can often be detrimental to individuals, may be the cause of these weird results. Researchers hypothesize this may partially explain why diets in general are failing.

A range of various factors like weight and age influenced a participant’s response to certain foods; however, surprising influencers included the composition and level of diversity found within their gut bacteria. Researchers hope to develop personalized diets by sequencing a patient’s microbiomes through stool samples.

The link between gut bacteria and weight loss

Since our gut bacteria affect our response to certain foods, they may also affect and potentially modulate our weight. Research by Jefferey Gordon, published in Nature, has shown that obesity can be transferred through mice in microbial transplants.

Major differences between obese and lean individuals in gut bacteria diversity have been observed, but only a few specific bacteria are known to play a role in overall health. Research continues to identify specific strains that may reduce the risk of developing obesity and aid in weight loss.

A new study, published in Cell, offers some potential clues after exposing mice to consistently cold temperatures (~43˚ F) for a month to imitate exercise.

The mice, in response to the cold environment, established a higher percentage of heat-generating, calorie-burning beige fat.

Despite consuming more food, the mice initially lost weight. However, the mice regained the weight after three weeks regardless of beige-fat percentages remaining high.

A potential answer was discovered when the mice were dissected: the researchers found the mice’s intestines grew in both size and surface area. Therefore, the mice were capable of absorbing additional energy from a fairly consistent food source. The larger intestines offset the initial weight loss that normally would result from higher beige fat percentages.

This extra energy was valuable for the mice as well as our ancestors. Living in a similar environment where calories are precious, a large, efficient intestine and improved energy absorption were likely competitive advantages. In modern society, however, this logic has changed significantly because we are not in need of food. Researchers believe obese individuals may have larger intestines than their leaner peers.

One surprising discovery from their research? Bacteria is believed to be the source of the mice’s larger intestines in colder conditions.

Of significance includes changes in the cold-induced mice linked to changes in their gut bacteria. For example, when bacteria was transplanted to germ-free mice, these mice also produced more beige fat and developed larger intestines.

A specific strain of bacteria, Akkermansia muciniphila, decreased significantly as mice exposed to cold temperatures developed larger intestines. However, when given A. muciniphila as a probiotic, the mice produced similar amounts of beige fat without experiencing larger intestines while also losing weight. This indicates A. muciniphila limited calorie absorption within the intestines.

The researchers believe this may suggest that specific strains may prevent caloric intake, thus controlling weight gain. However, this study was only done in mice, so it is important to understand that the results may not be reproduced in human studies because of our complexity.

The researchers involved with the study believe that the evidence indicates bacteria may influence weight. If this is true, scientists can potentially target specific bacteria to treat obesity and other diseases caused by it.

Zeevi, D., T. Korem, and N. Zmora, et al. "Personalized Nutrition by Prediction of Glycemic Responses." Cell 163.5 (2015): 1079-094; doi: http://dx.doi.org/10.1016/j.cell.2015.11.001

Chevalier, C., O. Stojanovic, C. Didier, et al. "Gut Microbiota Orchestrates Energy Homeostasis during Cold." Cell 163.6 (2015): 1360-374; doi: http://dx.doi.org/10.1016/j.cell.2015.11.004

Turnbaugh, P., Ley, R., Mahowald, M., et al. "An obesity-associated gut microbiome with increased capacity for energy harvest." Nature 444 (20016): 1027-031; doi: 10.1038/nature05414

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