Trust Your Gut to Make Food Choices? Maybe.
What if your body was purposefully sabotaging your chances at a healthy, better you? If your so-called second brain in the gut was deciding what you should eat so the bacteria there could thrive?
Like many people, I have been on the yo-yo path of dieting. I have suffered my way through Whole30s, I’ve counted the carbs, I’ve counted the points, and at this moment I’m even paying attention, albeit sometimes half-heartedly, to syns. If that makes no sense to you, it means you have yet to go down the path of Weight Watchers or Slimming World. For me, accountability from these groups is beneficial. But the diet plan? Not always. My cravings for certain foods has often overshadowed my well-reasoned health goals and it looks like my second-brain is the culprit.
What is this second-brain that I’m referring to? It is the microbiome in your gut.
There’s a two-way communication going on between your gut and your brain called the gut-brain axis (GBA). Research is steadily showing us that the gut microbiota (tiny organisms living inside you) are communicating with your brain in all areas including emotional and cognitive. Your immune system, metabolism, and even mental well-being are caught up in this GBA and many researchers feel this is the missing link to why some people can be food-focused and others are not. 
Westernized dietary patterns are known to be a major cause of the obesity epidemic, which also promotes a dysbiotic drift in the gut microbiota; this, in turn, seems to contribute to obesity-related complications. Experimental studies in animal models and, to a lesser extent, in humans suggest that the obesity-associated microbiota may contribute to the endocrine, neurochemical and inflammatory alterations underlying obesity and its comorbidities.
That can be a lot to digest (so punny!) so let’s break it down.
What is the typical western diet?
The Western pattern diet (WPD) is a modern dietary pattern that is generally characterized by high intakes of red and processed meat, pre-packaged foods, butter, fried foods, high-fat dairy products, eggs, refined grains, potatoes, corn (and corn syrup), and high-sugar drinks. This shift in diet was a fundamental lifestyle change due to farming practices and the industrial revolution.
By contrast, what is considered a healthy diet is fruits, nuts, vegetables, whole-grain foods, poultry, fish, and decreased processed foods. 
What is a dysbiotic drift?
Dys means bad, biotic means relating to living organisms. If your gut is drifting towards a dysbiotic state, it means your bad guys are outnumbering your good guys. You’re losing the protection that a healthy GBA offers you.
What does this have to do with cravings? Let’s say that Bad Guy 1 thrives on sugar. He loves sugar more than a toddler loves Mr. Blippi. We’re talking a major love of sugar. Sugar is what keeps his motor going, it is literally his life. He is going to keep sending messages to the brain for sugar, sugar, and more sugar. But, in this case, our person has decided to go on a Whole30 type of program and eliminate sugar for a month. What is our Bad Guy 1 going to do? Quietly die? No way. He is going to send many desperate messages to the brain for the host (you!) to eat sugar.
Sugar cravings are a symptom, not the problem. Choosing between the sugar-free yogurt for a snack compared to a doughnut can change your microbiota by influencing which ones live. As their population numbers change the signals to your brain also changes. Your cravings will change.
A few years ago, I did an elimination diet and cut out sugar and all processed grains. It was incredible to me to experience the vivid dreams of eating brownies, cookies, and more. My microbiota which had been used to a steady diet of processed food was losing its collective mind over the changes to fruits, vegetables and other whole foods. When I walked into the store, I could literally smell the sugar in the air in the cereal and baking aisles. If you ever want a quirky experience, go sugar free for a week! Eventually, my tastes shifted, and natural foods regained their intense flavours. Foods like grapes suddenly felt like eating dessert. Unfortunately, it didn’t take long for this to wear off when I returned to a typical western diet.
The microbes help the host’s brain decide what the body should eat by suppressing or increasing cravings. If your gut has shifted in a bad way, these signals are difficult to trust. Below I share actionable ways you can help your gut shift so it will work with you. However, there’s another player in the diet game other than cravings. It’s calories.
What if we don’t all use calories in the same way? Instead, it’s very likely that my microbes are extracting calories from my food in a different way than, say, my husband’s microbes. Researchers are investigating if we need to redefine calories based upon the studies showing this difference.
Although research on the microbiome is considered an emerging science, scientists already have made tremendous progress in understanding the microbial makeup of the microbiome and in associating microbiome diversity with human disease. Moreover, they are beginning to make headway in understanding how the microbiome impacts human health and disease. It is likely that much of this impact is mediated through diet. Growing evidence suggests that gut microbes influence what the human host is able to extract from its diet, both nutritionally and energetically. 
There is a lot of excitement over the idea of personalized diets to work with a person’s unique gut biome. The idea being a person could have their microbiome sampled and a dietician work with them to choose the optimal foods for maintaining a healthy weight and body.
A study on response to bread using a randomised crossover trial of one week long dietary interventions showed significant interpersonal variability in the glycaemic response to different bread types. The type of bread that induced the lower glycaemic response in each person could be predicted based solely on microbiome data collected before the intervention.
According to Turnbaugh, the results suggest that at least in the mouse model, the gut microbiome is “incredibly dynamic” and can respond to dietary perturbations very quickly. The researchers also found a significant effect of host diet on microbial gene abundance and expression. 
This is good news. It means what you decide to eat today can already start to make changes towards a healthier gut microbiome and, hopefully, decreased cravings.
Food changes to make today.
Although much of the confirmatory evidence comes from mouse models, long term weight gain (over 10 years) in humans correlates with low microbiota diversity, and this association is exacerbated by low dietary fibre intake. 
The recommended daily intake is 25 grams for women and 38 grams for men, however most people don’t even come close to that number. Some foods with high fiber include pears (5.5g), strawberries (3g per cup), apples (4.4g in medium size), carrots (3.6g per cup), lentils (15.6g per cooked cup), oats (16.5 per cup), sweet potatoes (3.8g medium sized).
What about gluten?
Animal and in vitro studies indicate that gluten-free bread reduces the microbiota dysbiosis seen in people with gluten sensitivity or coeliac disease. But most people who avoid gluten do not have coeliac disease or proved intolerance, and a recent large observational study showed an increased risk of heart disease in gluten avoiders, potentially because of the reduced consumption of whole grains. One study showed that 21 healthy people had substantially different gut microbiota profiles after four weeks on a gluten-free diet. Most people showed a lower abundance of several key beneficial microbe species. 
Above all, eat a wide range of plant-based foods to help foster a diverse microbiome. The microbes prefer different foods, so it is up to you to provide them.
Avoid highly processed foods, these are known to decrease the good bacteria and allow room for the bad ones to thrive.
Finally, be mindful of antibiotic use which kills the good and bad bacteria. Be sure to help your good guys replenish themselves by eating a lot of microbiome boosting foods after any rounds of antibiotics.
If you are interested in more information about the gut microbiome, please read my other article regareding gut health and exercise.
 Carabotti, Marilia et al. “The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems” Annals of gastroenterology vol. 28,2 (2015): 203–209. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/
 Institute of Medicine (US) Food Forum. The Human Microbiome, Diet, and Health: Workshop Summary. Washington (DC): National Academies Press (US); 2013. 4, Influence of the Microbiome on the Metabolism of Diet and Dietary Components. Available from: https://www.ncbi.nlm.nih.gov/books/NBK154098/
 Menni C, Jackson MA, et al. Gut microbiome diversity and high-fibre intake are related to lower long-term weight gain. Int J Obes (Lond)2017;41:1099–105. doi:10.1038/ijo.2017.66 pmid:28286339]
 Valdes Ana M, Walter Jens, Segal Eran, Spector Tim D. Role of the gut microbiota in nutrition and health BMJ 2018; 361 :k2179