COULD OBESITY BE TRANSMISSIBLE?

NUMEROUS ‘NON-COMMUNICABLE’ CONDITIONS MIGHT BE TRANSMISSIBLE VIA MICROBES, SCIENTISTS ARGUE IN PAPER

If a radical hypothesis being floated by scientists proves correct — that humans can spread heart disease, diabetes and other “non-communicable” conditions via unhealthy microbes in our guts — there might soon be a new question on dating apps: What’s your fecal profile?

In a paper appearing in this week’s issue of the journal Science, Canadian microbiologist Brett Finlay and colleagues point to growing data suggesting that cardiovascular disease, type 2 diabetes, irritable bowel syndrome and other diseases long considered not transmissible from one person to another might actually spread like stomach bugs.

“It really leads to a rather almost heretical postulate — that non-communicable diseases, which basically means non-infectious diseases, might actually be communicable,” said Finlay, a renowned microbiome researcher at the University of British Columbia.

“And, given that 70 per cent of the people in the world die of what we call non-communicable diseases, it gives you a whole different way of looking at these things.”

While still a hypothesis — and much more research is needed — where there’s smoke, there’s fire, Finlay said. “And there’s an awful lot of smoke.”

Writing in Science, he and fellow members of the Canadian Institute for Advanced Research build a compelling case.

First, people with chronic diseases tend to have a “dysbiotic” or different-than-normal gut microbiota compared to healthy people. Second, when stool from people with various non-communicable conditions, including heart disease, diabetes and obesity, is transplanted into healthy, germ-free mice — rodents raised in ultra-sterile environments — the animals develop the same diseases.

“Third, your microbes are more similar to the person you’re living with than the genetically related twin living on the other side of the world,” said Finlay, author of Let Them Eat Dirt: Saving Your Child From an Oversanitized World.

In a study published last March, researchers who analyzed gut and mouth bacteria from nearly 300 villagers living in the Fiji Islands found people living in the same households, and spouses in particular, had similar strains in their gut microbiota.

“You could basically figure out who was married to who based on the microbes,” said Finlay.

Non-communicable diseases account for 41 million of all deaths globally, but the sheer definition of an “NCD” rules out any kind of spread through microbes and focuses instead on genetic, environment and lifestyle factors, Finlay and the CIFAR team writes.

But there are trillions of bacteria, fungi and viruses living in and on the human body. One gram of feces, about the size of a fingertip, contains as many microbes as there are people on the planet, Finlay said.

These microscopic life forms play a role in digestion, immune response, metabolism, brain development and other functions. Most are in the lower gut, and some 80 million microbes can be transferred with a kiss alone, Finlay said. “Intimate contact for sure leads to spread of microbes.”

Obesity is, technically, not a non-communicable disease, but it is the leading risk factor for heart disease, type 2 diabetes “and pretty much every non-communicable disease you can list,” Finlay said. There’s also increasing evidence it has a microbial component.

Several studies in mice have found that thin mice can be made fat, and vice versa, with fecal transplants between obese and lean mice.

Obesity might also be transferable in humans: One 2007 study involving more than 12,000 people found that having an obese friend is associated with a 57 per cent higher chance of becoming obese.

Diabetes might also have a “communicable component,” the researchers wrote. Within a year of a diabetes diagnosis, spouses have a higher chance of developing diabetes themselves. Spouses of people with irritable bowel syndrome also have a higher rate of the disease than can be explained by chance alone.

He isn’t arguing that heart disease, diabetes or other non-communicable diseases are 100 per cent infectious. “It’s going to vary for different disease.” Moreover, it’s hard to untangle other factors. People might have a higher risk of obesity if a friend or spouse is obese, but is it because they’re now swapping gut bacteria, or sharing lifestyle habits? “I’m sure there will be naysayers and the hardest part is uncoupling environmental factors from microbial changes,” Finlay said.

For obvious ethical reasons, we also can’t transplant stool from a person with heart disease into a healthy person to see if their arteries suddenly start hardening. “But we need to recognize that microbes could be a contributing factor,” Finlay said, “which is a whole new way of looking at these diseases in terms of health policy and how we control them.”

There’s a positive light to all of this. “You can’t change your genes, but you can easily change your microbes,” Finlay said, through diet, exercise, probiotics, perhaps one day via fecal transfers, or even moving to another country. “Any environmental change results in a microbial change.”

INTIMATE CONTACT FOR SURE LEADS TO SPREAD OF MICROBES.