Nature or Nurture? Obesity Genes Outweigh Diet in Determining Health of Gut Microbes

Replication of obesity and associated signaling pathways through transfer of microbiota from obese prone rat. By Duca and colleagues. Diabetes, published ahead of print January 15, 2014

What is the problem and what is known about it so far?

The obesity epidemic is a global problem that is linked to type 2 diabetes, heart disease, and premature death. Fighting the epidemic is hindered by an incomplete understanding of obesity's causes. In recent years, researchers have discovered that the types of friendly bacteria (known as microbes) that live in the gut play a role in body weight, with some species of bacteria promoting weight gain while others are associated with a lean frame.

Why did the researchers do this particular study?

The researchers wanted to assess the relative influence of obesity genes versus diet on gut microbes.

Who was studied?

The researchers studied two strains of laboratory rats—obesity prone and obesity resistant—as well as mice grown under conditions that kept them microbe-free. The obesity-prone strain has a set of genes that make them more likely to develop obesity, while the obesity-resistant mice have genes that protect them from obesity.

How was the study done?

The researchers fed the obesity-prone and obesity-resistant rats the same high-fat diet. Then, they assessed the types of microbes in the rodents' guts. The researchers removed gut microbes from the rats and transferred them to the guts of the microbe-free mice. The subsequent health of those mice was tracked and analyzed to determine the effects of the microbes.

What did the researchers find?

After living on a high-fat diet, the obesity-prone rats had a different set of microbe species living in their guts than the obesity-resistant rats, with a higher proportion of the obesity-linked microbe species. The mice given the microbes from the obesity-prone rats gained more weight and developed more health problems than those given microbes from the obesity-resistant rats.

What were the limitations of the study?

This study was performed in animals, so it's difficult to know whether the results would be the same in the context of the human body.

What are the implications of the study?

Gut microbes have a powerful effect on health, regardless of diet. Eating too much fat may not matter as much as your genes in determining the healthiness of your gut microbes. Further research may indicate other ways—medications, eating more vegetables, or other approaches—to shift gut microbe populations to be healthier.

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