The motivations behind the choice of diet often revolve around improving body composition. There’s no problem with that, but diets have an impact beyond just helping us gain muscle or lose body fat. They also impact our gut health, which can have significant implications for our overall health. Around 400 B.C. The Greek physician and philosopher Hippocrates said “All disease begins in the gut.” Considering that up until the 19th century, doctors were still swearing the Hippocratic oath, and given that much of the Ancient Greek wisdom still influences today’s society in ways we don’t necessarily think about, we should give that statement the respect its due.
Many of today’s diets work on an exclusionary basis. Just look at ketogenic, carnivore, vegan/vegetarian, pescatarian, gluten-free, dairy-free, and low FODMAP. Each diet often removes entire food groups and reduces the overall variety of its nutritional profile. Having an ethical reason for choosing a diet is fine, but it’s important to know what implications that can have on your quality of life. So why does the variety of our diets matter so much?
Diet diversity & gut microbiome
Think of your gut microbiome like the Amazon rainforest. It has more species of plants, animals, and insects than we can name, and each plays a part in maintaining the efficient functioning of that biodiverse ecosystem. If a predator species is hunted to extinction, it will allow the population of its prey to increase, which can then reduce the population size of the organism next up on the food chain. This can then allow certain plant life to flourish, with potentially environmentally detrimental effects. A host of potentially harmful consequences, from the elimination of one species out of thousands.
Your gut microbiota has many metabolic functions such as the synthesis of vitamins (B12, K), allowing you to absorb calcium, manganese, and iron, and metabolising bile acid (needed to break down fats). It competes with harmful pathogens for nutrients, moves food along your digestive tract, and regulates your immune system. It can influence your response to chemotherapy and immunotherapy.
It’s a complex system. And that’s just a handful of what it does. When you start experimenting with extreme diets, you’re potentially removing important ‘species’ or introducing excessive amounts of new players into the environment that can impact its day-to-day functioning. A healthy lawn doesn’t take much care. If you don’t cut it too short, water it too much or let it dry, the healthy grass will always outgrow and outperform the weeds. When you start messing with it, that’s when you run into problems.
Popular Diets & Microbiome Diversity
Ketogenic diet: Almost fully eliminates carbohydrates from the diet (50g or less per day) so that the body starts producing ketones for energy use. It will also reduce the total bacteria abundance and diversity in your gut.
Western diet: Very pro-inflammatory, high amounts of fat, cholesterol, animal products, and sugars, often highly processed sources. Lower in fruits, vegetables, and whole grains. Usually high in sodium, which isn’t an issue if a diet is healthy, but in individuals who have diseases, can lead to further issues. Leads to a reduction in microbiota diversity.
Vegan/Vegetarian: Quite high in microbiota diversity and increased production of short-chain fatty acids (important for gut integrity, regulating blood pressure, and the immune system). They however don’t contain much BCAAS that we can take advantage of when it comes to building muscle and satiety.
Gluten-free: The abundance of healthy bacteria decreases through elimination, and there’s an increase in the number of potentially pathogenic bacteria such as E. Coli, and an erosion of the mucosal layer of our gut.
Mediterranean diet: Anti-inflammatory benefits, an increase in microbiota stability and diversity, an increase in healthy bacteria, and a decrease in potentially harmful bacteria. This diet as a baseline, with high protein, Omega-3s, probiotics, and fibre will do well for many people. Those with IBS, however, will have bad symptoms.
Fat loss diets: Any that places you in a caloric deficit will lead to a reduction in microbiota diversity over time, no matter how varied the diet. It’s important to take time to ‘give back’ to your body periodically to reduce the risks of developing gut issues. The reason many people report their digestive system feeling better on fat loss diets is due to the increase in lean protein, vegetables, and fibre, and a reduction in inflammatory foods that characterise a typical Western diet.
360° view of diets
Diets go beyond just calories in and calories out, though that’s the fundamental principle that determines body composition changes. You should now understand that any diet that promotes elimination or significant exclusion of food groups can have potentially harmful effects. While many are promoted under the guise of being healthy, often they’re just an outdated and debunked diet now sporting a new name trying to make a comeback for financial gain. Make sure to do your homework, and understand the potential trade-offs to make the most informed decision. A 6-pack may look cool, but it shouldn’t come at the cost of your health.
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