Over the past couple of years, there’s been a conversion in belief that the macronutrient source of food is more important than the quantity of food consumed when it comes to causing obesity. People like Gary Taubes have basically stated that high carbohydrate diets induce changes in metabolic hormones like insulin which essentially instruct the body to store energy in the form of fat… and he’s right. In his very popular yet incredibly boring book “Good Calories Bad Calories” Taubes cites studies showing nearly equal weight loss in people consuming high protein diets with either caloric excess or caloric deficit which is a pretty strong argument.
Other very smart people have responded by coming up with groups of people (notably the Kitavans) that eat pretty high carb diets and yet do not have signs of obesity or obesity-related diseases. Pretty good counterpoint in my opinion as well.
What gives????? How are these people eating high carb diets and not getting sick? Well for one, they are relatively active compared to most Western societies. Additionally, there may be genetic factors at work here as well that cannot be ruled out. However, another potential explanation is starting to emerge as well. For years now we’ve known that the human body gastrointestinal tract is literally covered in bacteria that we call “commensals.” In fact, its estimated that the human body contains 10X the number of bacteria in the GI tract as there are human cells in the rest of the body. These commensal bacteria grow both off of the food we consume as well as on products from the GI tissues such as mucus. In turn, our bodies use enzymes produced by the commensal bacteria to help break down and digest the food that we eat into usable energy sources. This symbiotic relationship is absolutely necessary for optimal health as we’ve recently learned using germ free (AKA bacteria free) studies in mice.
Well, recently we’ve learned that the bacteria that live in our GI tract are extremely responsive to the different types of foods that we eat. More importantly, these changes in the microbiota may be directly linked to changes in metabolic hormones that are involved in obesity, insulin resistance, etc.
The diets of the world we live in appear to modify the bacterial composition of the bacteria that live within our body. Instead of having benign commensals that really pose no threat to us or are anti-inflammatory, the modern diets induce the outgrowth of a higher percentage of inflammatory bacteria, namely gamma proteobacteria like E.coli and P.mirabilis. These “inflammatory” bacteria cause activation of the innate immune system causing low-level systemic inflammation which has been linked to everything from autoimmune disease, to allergies, to cancer AND insulin resistance!
Interestingly, the review above also cites studies showing that the innate immune system also seems to be able to sense nutrient excess as well, both through modulation of the microbiome but also through production of ligands that bind to the pattern recognition receptors that normally are built to detect pathogens.
So is it caloric excess or the quality of food that we consume which is responsible for obesity??? The answer (for now) appears to be both. I love this answer because it fits in so accurately with personal experience with clients. Most people do just fine by focusing on eating real foods and getting away from processed grains and artificial sweeteners. However, there are some people that really struggle to lose weight despite eating similar high quality foods. In my experience, these people are inadvertently eating way more calories than they thought they were… usually in the form of almonds and other nuts. I’m not saying that ALL of the reason they struggle to lose weight is as a result of the bacterial changes/immune activation but it cannot be ruled out as a contributing factor as well.
At the end of the day, focusing on eating non-processed food is a great place to start if you’re looking to improve your body composition and overall health. If you hit struggle to lose weight with this approach, then understanding how many total calories you’re eating is the next step as sometimes we can unintentionally consume way more calories than we really think we are eating.