Is Obesity Contagious? New Research Says Yes

two friends, talking, smiling, and eating popcornA few years back, a groundbreaking study of 12,000 people showed that your chances of becoming obese rise by 57% if you have friend who becomes obese. Originally, researchers thought this was mostly due to similar social and dietary habits shared by friends. Now, new research reveals the profound role of gut bacteria not only in obesity itself, but in its ability to be passed from person to person. It turns out that obesity might be not just socially contagious, but truly contagious … like catching a cold.

Gut Bacteria and Obesity

Researchers have been aware that obesity is related to gut bacteria for some time, and more recent research has also identified eight species of bacteria seemed protective against weight gain—all eight of which produce a short-chain fatty acid called butyrate. The highly respected nutrition expert, Dr. Michael Greger of, reported this month on the latest findings regarding obesity, gut bacteria, and transfer of bacteria from person to person, noting that the relationship is more complex than previously thought. Especially intricate is the way people share gut bacteria and thereby the propensity toward leanness or obesity.

Experimental evidence suggests that individuals raised in a household of skinny people may be protected against obesity. ~Dr. Michael Greger

black and white man and woman kissingResearchers have long understood that people who share close quarters also share more similar gut bacteria than those who live apart, but they weren’t sure why—they believed it could be due to similar diets, or due to the exchange of gut bacteria. Now, according to Dr. Greger, researchers have identified that “not only do cohabitating family members share bacteria with one another; they also share with their dogs, who are probably eating a different diet than they are.”

Not only that, but our homes “a distinct microbial fingerprint, and “just by swabbing the doorknobs, you can tell which family lives in which house,” Dr. Greger explains. Interestingly, if your family moves from one house to another, your new home will quickly shifts toward the microbial footprint of our old home. In other words, you bring your gut bacteria with you.

For more on the specific studies related to these findings, visit Dr. Greger at