According to a new study by researchers at the University of California, Berkeley and the University of Arizona, Tuscon, people living in cold climates have bacteria in their guts that prompts obesity.
It is known that obese people have a different proportion of microbes in their guts. They have more Firmicutes and fewer Bacteroidetes than those of normal weight. New research has discovered that people living in northern latitudes have more Firmicutes associated with obesity, and lower proportion of Bacteroidetes than people living farther south.
It is not clear why the microbe proportions differ however it could be that they have evolved with people in order to better extract energy from food in colder climates.
The researchers analysed the gut microbes of over a thousand people from around the world. The results showed that people living in the northern latitudes had more Firmicutes, the bacteria that is linked to obesity than those living farther south.
The comparison and analysis of six studies was published this month in the online journal Biology Letter by University of California Berkeley graduate Taichi Suzuki and Biology Professor Michael Worobey of the University of Arizona.
“People think obesity is a bad thing, but maybe in the past getting more fat and more energy from the diet might have been important to survival in cold places. Our gut microbes today might be influenced by our ancestors,” said Suzuki. One theory is that obesity linked bacteria helps to extract energy from food.
“This suggests that what we call ‘healthy microbiota’ may differ in different geographic regions.”
“This observation is pretty cool, but it is not clear why we are seeing the relationship we do with latitude,” Worobey said. “There is something amazing and weird going on with microbiomes.”
Professor Worobey found the results fascinating from an evolutionary biology perspective.
“Maybe changes to your gut community of bacteria are important for allowing populations to adapt to different environmental conditions in lots of animals, including humans,” he said.
Recently there have been many studies on gut microbes carried out among scientists as the amount of different bacteria and microorganisms in the gut seems to be linked with diabetes, obesity and cancer.
In obese people and obese mice the dominating group of bacteria are Firmicutes whilst in slimmer people and mice it is Bacteroidetes.
“Bergmann’s Rule — that body size increases with latitude for many animals — is a good one and presumed to be an adaptation for dealing with cold environments,” stated Suzuki’s advisor Michael Nachman, Professor of Integrative Biology and Director of UC Berkeley’s Museum of Vertebrate Zoology.
Suzuki has been carrying out studies on how rodents adapt to living at different latitudes.
“It was almost as a lark,” Woroby said. “Taichi thought that if Firmicutes and Bacteroidetes are linked to obesity, why not look at large scale trends in humans. When he came back with results that really showed there was something to it, it was quite a surprise.”
Suzuki used the data from six previous studies from 23 populations in Europe, North and South America, Asia and Europe. This data on gut microbes provided statistics of the numbers and types of bacteria and Archaea in peoples digestive system.
He discovered that the amount of Firmicutes increased with latitude and the amount of Bacteriodetes decreased with latitude despite of their gender and age.
The same patterns were found in African Americans as Europeans and North Americans. The patterns of Africans living in tropical areas were different.
Nachman said “Whether gut microbes also help explain Bergmann’s rule will require experimental tests, but Taichi’s discovery adds an intriguing and completely overlooked piece of the puzzle to this otherwise well-studied evolutionary pattern.”
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