A vaccine to prevent weight gain? It’s on the hori

BYLINE: Lisa Marshall

This time of year, millions of people turn to diets, exercise and medication to help them get their weight in check. 

New University of Colorado Boulder research suggests another surprising tool could help them achieve their resolution: Exposure to beneficial bacteria.

The study, published in the journal Brain, Behavior and Immunity, shows that animals injected weekly with a microorganism found in cow’s milk and soil were essentially immune to weight gain from a high-fat, high-sugar diet.

“What is so striking about this study is that we saw a complete prevention of diet-related weight gain in these animals,” said senior author Christopher Lowry, professor of integrative physiology. “This suggests that exposure to beneficial bacteria can protect us against some of the negative health outcomes of the typical Western diet.”

‘Old friends’ with new benefits

The study is the latest to report the benefits of healthy forms of bacteria known as “old friends” that evolved alongside humans but that we have lost touch with as we’ve moved from farms to more sterile, urban environments.

“As we have lost contact with these old friends that served to regulate our immune system and suppress inappropriate inflammation it has put us at higher risk for inflammatory diseases,” said Lowry.

In previous research, Lowry found that inoculation with an organism called Mycobacterium vaccae (M. vaccae), present in cow’s milk and soil, can prevent stress-induced inflammation and associated health problems in mice.

Those and subsequent findings have prompted Lowry to explore the idea of developing a “stress vaccine” derived from dirt-dwelling microbes.

For the new study, he and first author Luke Desmond, a PhD candidate in his lab, set out to determine whether M. vaccae could also help counter some of the brain inflammation and resulting anxiety that can come with a poor diet. 

One set of adolescent mice was fed standard, healthy chow for 10 weeks. The other consumed the rodent equivalent of Big Macs and fries, with 40% fat, 40% carbohydrates (half of them from sugar) and 20% protein.

Half of each group also got weekly injections of M. vaccae. 

All groups ate about the same number of calories, and all the mice gained some weight as they matured into adulthood.

As expected, the untreated junk food group began to gain significantly more weight at about six weeks than the healthy eaters. By study’s end, they weighed about 16% more than the healthy eaters and had significantly more visceral fat — the “bad fat” that collects around organs and can boost risk of heart disease and diabetes.

To Lowry and Desmond’s surprise, there was no difference in weight gain between the junk food group that got injections of good bacteria and the healthy eaters. The inoculated mice also had less “bad fat” at the study’s end.

“This finding suggests that M. vaccae effectively prevents the excessive weight gain induced by a Western-style diet,” said Desmond.

More research is needed to determine just how exposure to a bacteria found in dirt could prevent weight gain, and whether it can do so in people.

Lowry suspects M. vaccae may act directly on immune cells to tamp down inflammation, make fat healthier and boost metabolism.

He hopes to do more studies to determine whether M. vaccae taken orally has the same impact, and whether it could help someone who is already overweight lose weight. 

For now, Lowry says the best way to get exposed to helpful ‘old friends’ is to get out in nature, work in the garden and eat a variety of fresh vegetables (they soak up healthy microbes from soil).

Why not just ditch junk food? That’s easier said than done, he said.

“More than half of the food sold in grocery stores is junk food. It’s everywhere and it’s hard to avoid,” Lowry said. “If we can simply restore our exposure to these old friends, we could potentially prevent weight gain and other health impacts even in the presence of our terrible Western diet.”