In my new book, The Skinny Gut Diet, I talk at length about how gut microbes are in control of your health, and how your particular gut balance determines whether or not you will gain weight. Although it seems farfetched at first, everything seems to finally make sense once you realize that you are not entirely responsible for those extra 20 pounds.

Think about it: Who hasn’t been on an assortment of diets, only to gain back every pound—and then some? Or who hasn’t hit that dieting plateau when no matter what you do, the scale doesn’t budge? As it turns out, your gut bacteria may be to blame. That’s right—the fact that you are overweight may be the result of having the wrong bacteria in your gut.

In a fascinating review recently published in the journal BioEssays, researchers discuss evidence for the role bacteria play in triggering our food cravings. The bacteria in your gut need certain foods—particularly sugars and carbohydrates—that benefit them. So they trigger your cravings, causing you to overeat so that they can get the food they need.

“Bacteria within the gut are manipulative,” said Carlo Marley, PhD, one of the authors. “There is a diversity of interests represented in the microbiome, some aligned with our own dietary goals, and others not.”

Gut microbes work in four main ways to manipulate behavior and mood, leading to overeating and weight gain. Gut microbes:

  1. Alter communication with the nervous system via the vagus nerve (which connects the gut to the brain).
  2. Change taste receptors.
  3. Produce toxins to make us feel unwell.
  4. Release chemicals that make us feel good.

There is evidence that gut microbes have an effect on mood, a topic Dr. Smith and I have blogged about before. The researchers also discuss the ability of certain gut microbes to induce feelings of being unwell, which can trigger a person to overeat. One example they give of this phenomena is colic. Babies with colic have altered gut bacteria and are commonly overfed, which can lead to weight gain. Could it be that the gut microbes in these babies are simply trying to get fed? Scientists say yes. And other bacteria may be doing something similar in your gut.

“Gut microbes may manipulate eating behavior by hijacking their host’s nervous system,” stated the researchers.

Not only that, but many gut microbes produce neurotransmitters and hormones, such as serotonin (the feel-good hormone) and dopamine (the reward neurotransmitter). Many gut bacteria also produce compounds that are almost identical to leptin, ghrelin, peptide YY, and neuropeptide Y, all hormones that regulate satiety and hunger. The secretion of these compounds in the gut may affect how much you crave and how much you eat.

The researchers go on to discuss the effects of gut bacteria on weight gain, a topic I delve into in The Skinny Gut Diet, and we have also discussed here on the blog. They go on to discuss the use of probiotics for weight loss, as I do in the book and on this blog.

Interestingly, they discuss the possibility that a lower diversity of gut microbes is associated with more unhealthy eating behaviors. It’s a vicious cycle. When excess food is eaten, microbes have extra food to consume, which result in an increase in certain bacteria that favor those foods and a decrease in other bacteria. The dominant species then exert a stronger effect on the host (that’s you!) that leads to overeating, which further feeds the dominant species. This cycle lowers the overall diversity of gut microbes and leads to food cravings and weight gain. Yikes!

“Until we have a better understanding of the contributions and interactions between individual microbial taxa, it may be more effective to focus interventions on increasing microbial diversity in the gut,” note the researchers.

The good news is that you aren’t stuck with your bacteria. Gut bacteria respond quickly to changes in diet. To break the cycle, you will need to begin with your plate. Foods high in starches and sugars are the biggest culprits. Nonstarchy vegetables, low-sugar fruits, fermented foods, healthy fats, and protein will help you regain your gut balance, and your waistline. For more on how to do just that, consider ordering my book.