Are you one of those fortunate people who can eat anything you want and as much as you want and yet not gain weight? Perhaps you believe that you have been gifted with a “fast” metabolism and that your ability to process all types of unhealthy food is due to inherited genes passed on by your parents. Thanks to Mom and Dad, you are lean despite a voracious appetite.
But perhaps you fall in the opposite camp. Maybe you’re one of those unfortunates who, thanks to a set of less desirable genes, struggles with weight-gain despite a decent and healthy diet. Sometimes we blame our metabolism and we tell ourselves that it’s too “slow”. We’re convinced that we’ve been dealt a bad hand and that no matter what we do, food just seems to get processed differently in our bodies.
It’s natural for us to blame our genes. After all, how else can we explain the variability that we see in our responses to the same diet? I know people who have no problem consuming a triple-scoop banana split sundae without gaining an ounce of weight. Meanwhile, I’m not as lucky. When I eat the same dessert I can plan on spiking blood glucose levels, indigestion and an extra pound of weight when I step on the balance the next morning.
It turns out that you and I aren’t the only ones interested in understanding individual variability in our responses to diet. For years, scientists have spent huge amounts of time and resources attempting to identify the cause of this variability and effects on health. One of the best ways to measure genetic variability between individuals is to study identical twins. In the UK, scientists have been following over 10,000 identical twins in order to pinpoint the genetic and environmental factors that contribute to the development of disease.
So what have we learned from these studies? Well… despite what we might think (or what we might have been led to think), our genes may not be to blame for our weight loss woes after all and mom and dad may be off the hook. Study after study has shown that identical twins do not respond to diets in the same way. A pair of identical twins can eat the same exact diet with an equal number of calories and yet respond in drastically different ways (i.e., one twin might not gain any weight while the other may gain over 10 kg).
So what is going on here? It seems that scientists have been looking in the wrong place all along and the genes we inherit from our parents may not be to blame. We are all nearly identical in terms of our human genomes and up to 99.9% of our human DNA sequences are the same. Meanwhile, our microbiomes (i.e., the genetic material that makes up all of the microorganisms in our bodies) have 100-fold greater gene content than our human genomes and may be only 10% similar from one person to the next. Clearly, if one is looking for variation in diet response, then the real culprits may very well reside within our intestines in the form of the approximately 40 trillion microorganisms that make up our microbiota.
Recently, scientists performed a fascinating experiment on 800 people by continuously measuring their blood glucose levels following meal consumption for a week long period of time. They gathered measured response data on a whopping 46,000 meals and found high variability to identical meals, demonstrating that we all respond differently to food and that universal dietary recommendations can pretty much be thrown out the window. What’s good for you may not necessarily be good for me and vice versa. Even more fascinating, the researchers measured the gut microbiota for all of the 800 volunteers and discovered that the makeup of a person’s gut flora was a strong indicator for how that person responded to the food product. In other words, gut microbiota in individuals can make a food healthy for one person and unhealthy for another.
The researchers were even able to create an algorithm based on clinical data and microbiota composition in order to accurately predict how well a person responds to complex, real-life meals. In doing so, they were able to customize a diet plan that minimized post-meal blood glucose levels to ensure healthy eating on an individualized basis.
This work is a first step toward customized diet plans that, in the future, will allow us to tailor our diets in order to optimize health and longevity. As part of that future, we will likely be able to measure our microbiota in order know which foods are healthy to eat and which are not. Perhaps we will also be able to change our gut microbiota with probiotics, prebiotics and other natural supplements in order to ensure that the food we eat does not cause unhealthy spikes in blood glucose levels. To be clear, I’m not suggesting it will ever be possible to alter our microbiota in order to make a banana-split sundae a healthy meal (I wish!). However, I am suggesting a future wherein we will all be better informed regarding our individual responses to food.
Now that we know that our individualized gut microbiota plays a frontline role is determining how well we respond to food, what can we do to ensure optimized gut flora performance? First and foremost, it is important to foster a diverse gut microbiota by eating a variety of different natural and healthy foods. Scientific studies have shown that people with obesity and metabolic diseases such as diabetes have a lower diversity of species in their digestive systems. Our ancestors carried a much more diverse set of microorganisms and obesity was not the problem that it is today. Also of note, our ancestors ate approximately 150 different ingredients in a weeks-period of time while modern man, thanks to our advanced artificial refinement of foods, is lucky to consume only 20 ingredients.
No wonder our gut microbiota lacks diversity! We simply are not promoting an environment that encourages diversity and competitive feeding. Rather, too many of us restrict our diets to refined foods and allow a few bad species to overrun the other good species in our intestines. When this happens, we expose ourselves to inflammation, digestive distress, mood irregularities and other ailments that are caused by dysbiosis, which is a clinical term for microbial imbalance.
Reference:
Zeeti, D., et. al., 2015. Personalized Nutrition by Prediction of Glycemic Responses. Cell 163: 1079-1094.
About the author:
Douglas Toal, PhD is a Clinical Scientist with extensive knowledge and expertise in medical laboratory sciences, metabolism and anti-aging medicine.