Gut immunity dictates development of obesity when mice are fed high-fat diets, according to research published this week in Nature Immunology. These findings suggest that modulating the gut microbiota, either through probiotics, antibiotics or vaccination, may likewise alter the propensity to become obese in humans.
The familiar adage ‘You are what you eat’ may not be entirely true. Yang-Xin Fu and colleagues suggest that the host immune system is an active player in response to changes in diet. Normal mice fed a high-fat diet become obese as expected, but mice lacking lymphotoxin, a molecule that directs organization and survival of gut immune cells, remain lean on high-fat diets.
According to the authors, gut immune cells react to differences in ingested foods, leading to release of anti-microbial factors that alter resident microbial communities. Certain types of bacteria can survive in face of these immune responses and their abundance leads to weight gain. The authors conclude, therefore, that weight gain depends on the complex interaction between diet, immune cells and gut microbes.