What your diet needs is a little dirt.
It sounds like the beginning of an corny old joke: What do you get when you swap the gut bacteria of a fat mouse and a thin mouse? However, the answer provides a tantalizing clue to solving one of the most dire public health challenges of our time: the obesity epidemic. In a number of studies, scientists have manipulated the intestinal microflora in mice that are obese (A) and lean (B). What they have found is when A gets B's gut bacteria, it becomes a skinny mouse and the opposite is true as well.
Not enough research has been done on humans in long term trials to definitively prescribe how we should be using probiotics to maintain our healthiest weight, but there are plenty of encouraging findings. In a 2016 meta analysis that studied obese children, researchers found that, "short-term courses of probiotic mixtures containing...14 alive probiotic strains...were shown to reduce significantly total body and visceral adipose tissue weight, together with improvement in insulin sensitivity [a precursor to diabetes]." The same study outlined how probiotics can affect appetite, the ratio of lean body mass to fat, and metabolism. The right probiotics can also improve cholesterol.
Scientists say that to reap the health benefits of these microflora, we need to have a diverse array of strains thriving in our intestines—something that many Americans do not. Speaking with Fitness Magazine, Lee Riley, M.D., a professor of epidemiology at the University of California, Berkeley points out that the heavy use of antibiotics in the livestock industry over the last couple of decades has taken a toll on the fragile balance in all of our bodies. "The obesity epidemic really took off in the last 20 years in the U.S. So the question is, what happened then? What was a large segment of the population exposed to that could account for this massive weight gain?" He concludes, "Counties with the highest prevalence of obesity are those counties with large concentrated animal feeding operations." The overuse of human antibiotics and anti-bacterial cleaners has also dealt a blow to our systems. Fortunately, there are ways rebuild our individual microbiomes and help the little guys flourish.
Promoting a Healthy Gut
Create a healthy, happy internal environment by eating lots of prebiotics. These are the foods that gut bacteria love to eat. Fiber is especially important so aim to consume twenty to thirty grams a day. Fruit, vegetables, whole grains, nuts, seeds, and beans are loaded with fiber and have the added benefits of being nutrient-rich and filling you up without a lot of calories. Absolute microflora favorites? Bananas, onions, garlic, leeks, asparagus, artichokes, soybeans, sweet potatoes, and whole-wheat products.
Eat a variety of probiotics. We know that different strains of bacteria are linked to healthy weight, so aim for diversity. Don't rely solely on supplements, they aren't regulated by the F.D.A. for efficacy and safety. If you do want to try a supplement, experts recommend looking for one that contains these strains: Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus brevis, Bifidobacterium lactis (B. animalis), and Bifidobacterium longum. The best, cheapest, and easiest way to ingest probiotics is by simply by eating a range of cultured and fermented foods such as tempeh, yogurt, kimchi, sauerkraut, miso, and kombucha.
Some experts promote eating more soil based organisms, which can be found in supplements and are purportedly hardier and better able to pass through the acidic stomach to the intestine. Writing for Scientific American, nutritionist Monica Reinagel outlines her steps for restoring a healthy gut post-colonoscopy, which include eating raw vegetables from her own garden that are only lightly rinsed to remove the grit.
Sugar is the enemy. Sugar and refined carbs are absorbed very quickly and essentially starve our intestinal flora. Unhealthy organisms such as fungus and yeast also thrive on sugar. All in all, a dire situation for cultivating the best gut bugs.
While the science of gut bacteria and human health is cutting edge, you still can use common sense to guide your eating habits. What we keep learning over and over is that there is no miracle formula for weight loss that will allow us to consume junk and be slim and healthy. You have heard it a million times before: avoid processed foods, use sugar sparingly, load your plate with fresh vegetables and other whole foods, and eat some yogurt.