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Why I Don't Rely On Genetic Testing for Fitness

March 14, 202411 min read

Before I inevitably step on anyone’s DNA test-loving toes, let me preface this by saying that I’m not discouraging DNA testing if that’s what one wants to do. If it truly provides you some insight for the better, especially for medical reasons, then great. I’m simply letting readers know why I personally don’t, what negative impacts there may be, and that I think it’s fair to let people know they don’t have to rely on these tests to obtain greater health and fitness.

1)     The main reason- EPIGENETICS…

Shortly after becoming a mom, I took my fitness knowledge into a different space and started learning about our minds and how external factors influence our internal health. I began learning about this budding branch of science called epigenetics. Epigenetics is the study of how our genes are expressed, despite how they’re originally coded. Why does this matter? Because our lifestyle can and does alter our gene expression. In other words, just because you’re predisposed to or possess a certain gene, doesn’t mean it’s expressed, or that your lifestyle can’t change or “turn off” the expression of that gene. And unfortunately, these DNA tests don’t tell you what genes are or are not expressed. This matters!

This is why identical twins can respond differently to the same diet, and why you may get a DNA report with things that seem to contradict what you observe. I recently read a blog post by Michael Kummer, who mentions this regarding his DNA testing results. He addresses several aspects of his results- some he can vouch for, while others make less sense. According to the test results, for example, his body should do well with more carbohydrates and less fats. However, he tends to follow a ketogenic dietary lifestyle and performs and feels great in doing so.

So why is this? Well, he’s likely conditioned his body to his preferences over the years, despite his original DNA. And this makes sense when you study biology and how living organisms evolve and adapt to ultimately survive. What’s available to you for years and years may not technically line up with what your original DNA code dictates, so it would be silly to reason that the only way to thrive is to match your DNA code for what it is, despite how you may have already adapted to other dietary habits and ways of living that have influenced gene expression over time.

I personally would like my body to be as malleable and adaptable as possible. I don’t want my body’s functionality to fit inside a preconceived box regarding DNA. That’s not how we were biologically designed. Just because we “know” more doesn’t always mean it’s useful.

BOTTOM LINE: Fitness, nutrition, and your body’s response to it goes beyond the original coding sequence- your daily choices can affect your genetic expression beyond what was given to you at birth (and actually, parental choices can even affect a growing fetus’ gene expression too- you can read up on that as well). So, in short, your DNA report is not gospel truth. By “taking out the guesswork,” you may actually be creating more guesswork or confusion.

2)     This area of science is still relatively new…

There are some things with an established amount of certainty as it relates to linking certain genes to risk factors. However, while nutrigenetics and nutrigenomics seem promising, these areas of study are still highly based on preliminary data (vs multiple or repeated trials) and correlation (vs actual causation), and can therefore be oftentimes conflicting. Humans have only scratched this surface- there is still so much we don’t know in regards to nutrition. Again, multiple factors continuously influence our gene expression, including ethnicity, nutrient availability, preferences and existing habits, and malnutrition. Add to that using the “general population” for establishing nutrition recommendations, which are often used as a baseline for spitting out health and fitness results. (Things that make you go “hmmm”…). This is why these reports will often use words such as “likely” or “may be.” What I also find interesting is how they tend to still lean toward general recommendations, while telling you what’s “best.” But hey, presentation is everything, right?

BOTTOM LINE: Reliability and scientific certainty, therefore, is still significantly lacking. There will undoubtedly be outliers. While we are certainly all individuals, and I’ve never preached a one-size-fits-all approach to fitness, science has still shown little evidence in favor of genetic-based diets being paramount to a generally balanced one. Hair follicle and other food sensitivity tests also tend to be unreliable and can result in false positives, leading to unnecessary elimination of foods from one’s diet. We have a long way to go before we settle for making life-altering decisions based solely on genetic testing.


3)     We can’t “unknow” things…

I love knowledge- I love knowing things. I thrive on knowing things and learning new things. But… I also know when I don’t need to know things, or when knowing things may potentially be more damaging than beneficial. More people today would do well making a conscious effort at having a healthy balance in this area. DNA testing, regardless of its purpose, can frankly mess with your head. Let me be clear… I do believe technology is a beautiful thing, and I do believe that DNA testing can be a blessing for some in regard to being proactive. However, let’s say you read something in a DNA report that claims you’re high risk for certain things, so now you’re constantly dwelling on it. Is it really helping you now? Is it really bringing you to a healthier place now? When we hyper-focus on something, it tends to manifest, whether it’s good or bad. Or again, your report may suggest something contradictory to what you’ve lived tried and true for years and feel great doing. So are you going to flip a 180 and try something different just because it’s on that paper? In that case you’re likely better off sticking to what’s actually working for you. Your direct observations trump all. What your original DNA says may not actually match up to what’s actually happening in real time. Just because you’re allegedly below or above “average,” does not mean that isn’t normal for you. This is good to know on lab work as well, and a good practitioner can interpret things accordingly.

BOTTOM LINE: Before you seek to know more, know your own mental and emotional capacity for acquiring new information. Weigh the risk vs benefit. Put it into perspective for you personally.

4)     Sustainability matters more than most care to acknowledge…

Oftentimes I’ll remind people how important adherence and sustainability are- that you can have the best fitness and nutrition programs on a platter, but if you can’t or won’t adhere to those programs and sustain results, it doesn’t even matter. Likewise, you can acquire all the knowledge that modern geneticists have to offer about your DNA makeup and suggested style of living, but what does it matter if you can’t adhere to and sustain whatever that calls for?

BOTTOM LINE: What’s realistic shouldn’t be discounted.


5)     Observation is key in any science experiment, and it’s key to your own health and fitness too…


If you want to know whether you absorb a certain micronutrient well, check your labs. It’s usually pretty easy to tell where you’re actually currently lacking by regularly testing markers while eating a balanced diet, and observing how you feel in relation to that. If your levels are consistently normal and you’ve experienced no such symptoms to indicate otherwise, you do not need to supplement just because a DNA report told you to. If you’re consistently consuming a balanced diet with adequate calories for fuel and not spending much time in a calorie deficit, you’re more than likely a-okay, especially if you’re taking a quality multi-vitamin and fish oil daily to fill in potential gaps.

If you want to know what kind of training and exercise your body responds best to, get up and go try them out! Even better, again- keep up with regular lab work while doing so. You’ll see what positively or negatively affects what. If you’re periodizing your strength training as you should be, and you’re working in generally appropriate amounts of cardio, and you’ve tried different training styles, and you’ve been eating and fueling appropriately, and you’re tracking and observing how your body composition responds as you go, it really won’t take long to figure this out, along with determining what you actually enjoy doing regardless (because no one wants to just spend all their time doing things they hate, but you may also need to adjust to make things work for you too).

If you want to know how sensitive you are to the sun, get out in the sun! I promise, you’ll figure it out soon enough. You probably figured it out before you lost your first baby tooth. Most of us can accurately gauge our limits to sun exposure as our bodies were created to give us some signs. I know my fair skin and light features make me sun sensitive- if I’m out in the sun for any prolonged period, regardless of season and temperature, I feel ill later. I get a reasonable amount of sun exposure, I supplement with Vitamin D, and it has never been an issue. Moving on.

If blood sugar is an issue for you and you want to know your insulin sensitivity with different training styles, test your glucose levels around different training styles and compare it to how you’re feeling. What you actually observe may differ from what “should” be happening.

If you’re mentally consumed with fat vs carb utilization, you can probably just disregard whatever the report says here, because science has shown over and over that this is more preferential. You’re going to utilize what’s available. You burned more fat on a high fat diet? Congratulations- it’s because you’re EATING more fat TO burn. When overall daily calories and protein are equated, there is little to no difference in effectiveness between a high fat/low carb or low fat/high carb macronutrient distribution, leaving this mostly to preference.

If you want to know how tolerant you are to caffeine, drink more than one cup. Drink a cup in the afternoon or evening. Palpitations? Wide awake all night? Terrible sleep? You’re probably not that tolerant. Make your life decisions accordingly.

An interesting part of these, to me, is intrinsic motivation and addictive behavior. But again, we’ve probably all pegged ourselves on both of these by the adolescence years.

BOTTOM LINE: You don’t HAVE to spend $100+ on DNA testing to tell you how you were coded and how you should be responding to stimuli. Get to doing and observing. There is more value in observation than blindly following DNA testing results based on limited averages and basic ranges. Ideally, I would simply suggest having some years of various fitness and nutrition lifestyle experience under your belt before taking such a DNA test for a reasonable comparison. At best, DNA reports can serve as a guide.

Again, I’m not here to discourage or dissuade anyone from DNA testing for their health and fitness. But I am saying it’s not the most useful approach, and it’s fair to know that you can and do control quite a few variables, and what a piece of paper (or email, whatever) says does not necessarily define how you should approach your individual journey. If your results say that longer endurance training is “best” for you, but you have minimal time to work out and genuinely enjoy shorter bouts of strength training more, you will absolutely get better overall results with time focusing on strength training vs trying to spend more valuable time on something you don’t enjoy and are less likely to continue. That’s a waste. Too many people do this, get discouraged, and quit.

All of this said, I would venture to say that while DNA testing has its place with regard to certain genetic disorders and diseases, the impact it has on the minute details of how you train and eat is still less than exceptional. An overall healthier lifestyle that you can adhere to, sustain, and also enjoy regardless of the DNA hand you were dealt will mitigate a multitude of preventable illnesses across your lifespan.

So, if you’re trying to decipher one of these things, know that it’s only information, generated according to what we currently know (or think we know) so far. And also, if you’ve been in the fitness space a while, it’s not likely to tell you any hugely revolutionary insight that actually makes sense. If you do choose to use DNA testing in regard to fitness and nutrition, just understand what you’re reading, what it means for you, how it actually fits your life, and have realistic expectations if and when making lifestyle changes according to your results. And like I said, confirm things (true or false) with proper workup (i.e. labs).

Just remember- our DNA is malleable, therefore our lifestyle and environment influence it throughout our life. This is why it’s so important to make healthy choices- for our own outcomes AND those that come after us in the sequence.

Keep shining!

Your trainer and coach,



Some sources I’ve linked in the text and further good reads:

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Kandis Joubert

Kandis Joubert is a NASM-certified personal trainer and nutrition coach, specializing in corrective exercise and fitness nutrition.

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