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Genetic Diets and Fitness Plans

Are They Ready for Prime Time?

By Gary F. Zeolla


      The rage in the diet and fitness industry in the past few years is genetic diets and fitness plans. These are diet and exercise plans based on one’s own genes (or DNA).

      The testing of a person’s genetic code is now relatively easy, and many people have used that fact to have their ancestry tested. Determining a person’s heritage from their genes is rather straightforward, and different services will probably yield similar results. But what about recommending how a person eats based on their genes. Or how they should exercise? Is that as accurate as heritage testing?


The Methodology and Results


      As with heritage genetic tests, for a diet and fitness genetic test, you generally swab your inner cheek and send the sample into the company. Then a few weeks later, they will send you detailed results of what your DNA shows Most companies will test for 100,000s of genetic markers.

      Those markers are then compared to what scientific tests show a particular marker is correlated with. Thus, for instance, a particular genetic marker has been shown in a research study to be linked with celiac disease, the inability to digest gluten, a protein in wheat, rye, and barley. Thus, the company will tell you that you are “likely” to have celiac disease, so you should avoid those grains.

      The same will be done to give you recommendations on what percentage of macronutrients (fat, carbohydrates, and protein) would be best for you to consume. This will then let you know if you are best off with a low-fat diet, a low-carbohydrate (carb) diet, or something in-between.

      Some will even dig deeper and tell you what types of fats and carbs you are best consuming, with suggested percentages for monounsaturated fats, polyunsaturated fats, and saturated fats and simple versus complex carbs. And there might even be recommendations on your intake levels for various vitamins and minerals. And some might tell you how often you should eat each day. They might even tell you how many servings of each food group to eat each day and maybe even specific foods recommendations.

      In regard to fitness, the main result has to do with a person’s muscle fiber type. There are two main types: muscle fibers for endurance and muscle fibers for power. The technical terms are Type I (or slow twitch) fibers and Type II (or fast twitch) fibers, respectively. The latter type is further divided into subcategories, using different labels. But those nuances don’t concern us here. What matters is the difference between Type I and Type II fibers.

      Most people have about a 50/50 split of Type I and Type II fibers. However, an elite endurance athlete, like a marathon runner, will probably have a much higher percentage of Type I fibers versus Type II, like an 80/20 split, while an elite power athlete, like a powerlifter, will probably have a higher percentage of Type II fibers, like a 20/80 split.

      Other fitness results from these tests might tell you how often a week you should work out, the amount of volume you need, how much rest you need, and your likelihood to get injured in various ways.

      Some tests will also give you recommendations in other health areas, such as how much sleep you need, how well you tend to handle stress, and your risk factor for various degenerative diseases, like Alzheimer’s Disease, cancer, heart disease, Parkinson’s Disease, and many others.


The Cost


      These tests are not cheap. The ones I looked at range from $89 to over $250, depending on the company. The cost will also vary depending on if you are only testing for diet, or if you are also testing for fitness and other health risk factors and even for ancestry. If you already did the latter, you might be able to use that sample to get a reduced rate for a diet and fitness genetic test. But even at that, these genetic tests cost a lot of money. But are they worth it? To answer that question requires answering a more fundamental one.


Are the Recommendations Accurate?


      How do the services arrive at the recommendations based on your DNA? The genetic test itself is rather straightforward. It is now easy to determine various genetic markers. But how do the companies know a particular genetic marker indicates, for instance, that a particular person should follow a low-carb diet? It comes from a correlation of that genetic marker with research studies.

      To explain, a study will look at how well people do on a low-carb versus a low-fat diet and compare that with various studied genetic markers. Or they will try to find a correlation between how well people handle carbs and various genetic markers. Namely, they try to find a particular genetic marker for those who have a higher than normal blood sugar response to eating carbs. Then if you have these markers, the service will say you are better off eating a low carb diet.

      But there is the rub. How accurate is the research study the recommendation is based on? The answer to this question begins with looking at the study itself. How many people were included in the study? How long did it last? Were the results statistically significant? Who paid for the study? Who conducted the study? Who were they study participants?

      A study that involved ten people and lasted for ten weeks is far different from a study that included 100,000 people and lasted for ten years. If you’re being told to limit your carbs based on a study like the former, then you might limiting carbs for little reason. That study might be proven to not be accurate when a study like the latter is later done.

      Moreover, a study looking at the health effects of red meat intake that is funded by the meat industry might yield different results than one funded by a grain-growers association. There could be a bias towards recommending low-carb diets with the former and high-carb diets with the latter.

      In addition, some studies use Olympic athletes as their test subjects. Results from such studies might not be applicable to the Average Joe or Jane.

      Then there is the recommendation itself. Just because a particular marker indicates a person might have a greater blood sugar response to carbs than normal, does that mean those with that marker should avoid all carbs or just high glycemic ones? There is a far different glycemic response to oatmeal than to a puffy, sugar-coated cold cereal.

      Moreover, rather than having a genetic test to see if you might have a higher risk of overreacting to carb intake, it would be better to have an actual blood sugar response test (aka, glucose tolerance or load test) done. Similarly, rather than being told your DNA indicates you are “likely” to have celiac disease, it would be better to have a blood test or colonoscopy performed that can tell you for certain if you do or not.

      Adding to these problems is to date there have not been that many tests done comparing DNA markers with various health effects, and the ones that have been done are usually smaller studies that did not last very long. But if the recommendation is based on just one such study, it might not be accurate and proven to false in latter studies. Moreover, some companies might use different studies than others. That is why you might get exact opposite recommendations for the same genetic markers if you have tests done by more than one company.


General Recommendations


      To confound the problem, many times the recommendations are so general so as to defy the idea that what you are getting is a diet and exercise planned tailored to your specific genes. A “sample report” I looked at for one service says that based on that sample person’s DNA, he should eat each day: four servings of vegetables, two servings of fruit, two servings of meat or a protein equivalent, and 2-3 servings of dairy.

      As I looked at that, I knew it looked familiar. Then it dawned on me—that is basically the USDA’s old recommendations in its “Four Basic Food Groups” that preceded the “Food Pyramid” that preceded today’s “MyPlate.” All that as missing is the recommended four servings of grains. In other words, the recommendation was not that tailored made but just a slight modification of an old recommendation for all Americans.

      In s sample fitness report, it said the sample person was at an elevated risk to tendon injury. The recommendation? Do stretching exercises. Again, that is basic fitness advice that would apply to anyone who exercises regardless of their specific genes.

      It would seem recommendations based one’s genes do not change basic health advice that much, so why pay $200 for it?


Specific Foods


      Some services will give you a list of recommended foods based on your “unique” dietary needs. The idea is, the listed foods are good sources of the nutrients your genes say you have a high need of. Thus, if your test says you have a high need for say zinc, then they will give you a list of foods high in zinc.

      But what is meant by a “high need” is not clear. The USDA’s Recommended Dietary Allowances (RDAs) for vitamins and miners are set so as to cover 97-98% of the population. As such, your need for zinc would almost certainly fall below the RDA. Thus, if you are consuming the recommended amount, you should be just fine. And the truth is, most Americans consume more than the recommended levels for most nutrients, no matter what supplement companies might tell you.

      But for our discussion, you can easily determine how much of various vitamins and minerals you are consuming by keeping track of your diet for a few days with any one of the many diet apps now available. If you do fall below the recommended amounts, then the app will probably be able to give you a list of foods high in that nutrient. At least, the program I use, Diet Power, will do that. And it is a free app that will do it for free. No need to spend $200 for such a list.

      It also must be noted that a DNA test will not be able to tell you if you are allergic to any foods. For that, you will need to consult an immunologist. And again, a genetic test can only tell you if you are “likely” to have food intolerances like celiac or lactose intolerance. It cannot tell you for certain. For that, you need to consult a doctor who can give you the specific test.

      The point is, in that list of recommended foods might be foods you are allergic or intolerant to, so it will not do you much good. It simply is not that specialized to your unique body.

      Moreover, a DNA test will not consider alterations for nutrient needs due to your exercise habits or any health conditions you might suffer from. It also does not consider your unique health goals. Thus, for instance, if you are weight training with the specific goal of adding muscular body mass, the genetic test will not account for the extra protein and calories that such a goal requires.


Born or Made?


      An age-old question in sports is, “Are athletes born or made?” My answer to this question has always been “Yes,” meaning, “Both.” Some people are naturally more athletic than others. That is a clear fact that any schoolyard pickup game will attest to. The kids know who the better athletes are and who are not so athletic, and the former will get picked first and the latter last.

      However, those naturally gifted children, if they do not train and practice, will never excel. And those who are not so gifted, if they train hard and practice, can do quite well in their chosen sport and even surpass the lazy naturally gifted athlete.

      The point is, genetics is not destiny. Genetics do matter, but “environment” can override genetics. Consider, for instance, the issue of muscle fiber type. Again, elite endurance athletes tend to have a higher percentage of Type I fibers, while elite power athletes tend to have a higher percentage of Type II fibers. But there is evidence that training can change one’s muscle fiber type.

      In other words, the reason elite endurance athletes have a higher percentage of Type I fibers is not necessarily because they were born that way. It could be that years of long-distance running has caused some Type II fibers to convert to Type I. The reverse would be true for the elite power athlete. Years of weight training have caused the muscle fibers of the elite powerlifter to convert from Type I to Type II (Elite).

      Similarly, you might not be genetically disposed to consuming a high fat diet, but if you have been doing so for many years, it is possible your body has adapted to that kind of diet. As a result, if you tried a low-fat diet, you might feel quite awful, at least initially, until your body adapts to the new diet.

      This phenomenon can especially be seen in the longtime vegetarian or vegan. After years of not eating animal foods, a vegan can become quite sick when consuming animal foods, despite a DNA test result that showed they would be better off with a higher protein diet that is best attained by eating animal foods.


Now What?


      The last point leads to the next. If you spend the money on a genetic test, are you prepared to make radical changes to your diet or lifestyle if the test says you would be better off doing something different from what you are currently doing?

      Using the last example, if you are a vegetarian or vegan, would a genetic test saying you are better off with a high protein diet override the reasons you became a vegetarian in the first place and lead you to eat meat? If not, then why bother with the test? Or if you are Italian and love pasta, but the test tells you that you are better off with a low-carb diet, would you be willing to give up your pasta?

      The point is, Americans by and large know what a healthy diet entails, but they are not following it. Take one basic dietary recommendation that would be true no matter what your DNA—eat more vegetables. You know you should, but do you? Do you eat at least four servings of vegetables a day? If not, why not? If you cannot follow that one piece of health advice, will paying $200 for a DNA test cause you to do so?

      I’m saying this as the Standard American Diet is SAD. What Americans consume is far from the general health recommendations that most authorities would agree upon, regardless of the particular type of diet they advocate, as I detail in my book Creationist Diet: Second Edition. Since Americans do not follow that advice, I am doubtful they will follow the advice of a genetic test.

      On the fitness side, Americans know they should exercise regularly, but few do. Again, will a genetic test change that? I doubt it.

      Or if you do exercise, but your exercise of choice is say long distance running, and the test says you would be better off lifting weights, will you give up your long runs in the fresh air and sunshine and start working out in a dark, drab, dusty gym?

      For example, I have been telling a younger relative of mine for the past decade that he would make a great powerlifter. I’ve been saying that, as he takes after me, having the body build of a powerlifter, probably even more so than me. But I’ve never been able to get him interested in competing. He recently had a genetic test done, and it confirmed he had “the muscle fibers of an elite powerlifter.” Did that confirmation of my observation give him the incentive to start competing? Nope. His sister even asked him, “What are you going to do with your elite powerlifting genes?” His response? “Waste them” (much to my chagrin). But the reason is, he has other priorities in his life that preclude him from dedicating the time and effort it takes to become an elite powerlifter.

      Again, genetics is not destiny. We all make choices based on many factors other than just our genes. As Americans, we have that freedom. But if my relative had lived in an old Soviet bloc country or maybe even in China today, he might be forced into some form of power training, as those oppressive governments would not let him “waste” those power genes. And if the American government turns oppressive, the same could happen here.

      Be that as it may, to use a more serious issue, if a test says you are likely to contract a serious degenerative disease, what will be the outcome of that knowledge? In some cases, there might be simple changes you can make to your lifestyle that will reduce your risk of that disease, but chances are, they are changes you already known you should make.

      At a higher risk of heart disease or cancer? The recommendations will be to eat a healthy diet, which again will certainly include eating more vegetables, and to start exercising. If you’re not doing that already, will you start doing so because of the test?

      In some cases, reducing your risk might require much more radical steps. For instance, in 2013, Angelina Jolie, “underwent a preventive double mastectomy after learning that she carries a mutation of the BRCA1 gene, which sharply increases her risk of developing breast cancer and ovarian cancer” (CNN). Would you do the same? Would you whack off body parts that are currently perfectly healthy due to some test?

      But then, if the government takes over the health care industry as many seem to want, then maybe you won’t have any choice. Women with such markers might be forced to have a double mastectomy, and men with prostate cancer markers might be forced to have a prostatectomy, as it would be cheaper to cut off those body parts now before they are cancerous than to treat the cancer later, never mind that the women are left disfigured and the men are left with urinary incontinence and impotence.

      In other cases, there is little you can do. If the test says you are a high risk of Alzheimer’s Disease or dementia, what are you going to do with that information? There is little that can be done to prevent those disease, other than again, basic health recommendations about following a healthy diet and keeping physically and mentally active. If you’re not doing that already, then will the test cause you to do so? Or will it just cause you to fret over something you can do little about?

      My point is, you probably already know in general what you need to do to stay healthy. If not, then books like my Creationist Diet and God-given Eating Plan will give you that information. But will you follow it? If not, then will a genetic test that is far more expensive than a book cause you to do so?

      If it does, then that might be the main value to a genetic health test. If not, then it is just a waste of money, or worse. If the test says you are at high risk of developing something you can do little to prevent, will that just cause you undo stress worrying about it? If so, then you would probably be better off just not knowing.

      That would especially be the case if your health or life insurance company found out about your high risk for a degenerative disease. Could they jack up your rates due to your higher risk, or maybe deny care for a current problem on the basis that you will die of that disease later anyway?


My Decision


      If I sound unduly harsh about these genetic tests, that is because, when I began to investigate them, I was very disappointed by what they currently offer. I thought they might be the way to answer some lingeringly questions I have about my own diet and exercise program.

      For the most part, I have been above to figure out what works best for me based on what the Bible and scientific evidence teaches in regard to diet and exercise. I outline that research in my two books on nutrition and the Bible in the hope that my research and what works for me might be a help to others in figuring out what works best for them. And I thought these tests would help me and others to narrow down the possibilities within that framework.

      But as they stand today, these tests do not. The dietary and fitness advice is based on too flimsy of evidence and is too general to be helpful beyond what you will get from books like mine. Simply put, these genetic tests are not ready for primetime. Maybe in 5-10 years the situation will be different. But for now, after researching out these types of tests, I decided to not waste money on them for diet and fitness advice.

      As for the tests for risks of degenerative diseases, I already known which disease I am at risk for from my family history, and I am already doing what little can be done to reduce my risk for those maladies. Confirming that I am at risk for them would not lead me to do anything I am not already doing, except to cause me to fret unduly over the possibility of contracting one of those diseases.

      As for ancestry, I’ve never cared much about that. I know my father is Italian, and my mom is half Slovak. My mom’s other half (from her father) is a bit up in the air, but I really couldn’t care less. And if I did care, I would just check my brother’s test results, who had an ancestry test done a while ago, as my results would be the same as his.

      But for me, I am an American and a Christian. That is all I need to know. I have never identified myself as an Italian-American or a Slovakian-American or whatever. As far as I am concerned, identifying people as hyphenated Americas is just one more way of Tearing the USA Apart. Let’s just call ourselves Americans and leave it at that.

      The only thing I might find interesting would be finding out what is my percentage of Type I versus Type II muscle fibers. Given my proficiency in powerlifting, I would assume I have more of the latter than the former, but it would be interesting to know the exact percentage. But again, whatever the percentage, there would be no way of knowing if I was born with that percentage or if it has been modified by decades of powerlifting training.

      And whatever the percentage, it would not change what I am already doing. Even if by some strange twist of fate, I found out I actually have more Type I fibers than Type II fibers and thus would be better suited for marathons than powerlifting, there is no way I would abandon my powerlifting training and take up long distance running, as I find running to be intolerably boring, while I very much enjoy powerlifting.

      Finally, my decision not to use one of these dietary, fitness, or even ancestry genetic services relates to concerns over what they will do with my DNA sample when they are done with it. Some companies promise to destroy it, but will they? The fact that you can get a reduced rate for a diet and fitness test if you already had an ancestry test done shows that the ancestry company did not destroy the sample but still have it to forward it to another company.

      Could my DNA end up in the hands of the federal government or my health or life insurance company, and could that come back to bite me in the form of forced preventative treatments, higher insurance premiums, or denial of health services? Or might I be forced to do something I don’t want to do because my genes say I am “suited” for it? Such are legitimate concerns that many do not even think about when freely sending in their DNA to a company they know little about.




      Whatever the case with me, the reader will have to decide what you think is best for you. If you have $200 to waste, then go ahead and blow it on one of these genetic tests. If the results give you an incentive to start consuming a healthy diet and to start exercising, then it might be worth it.

      But if finances are tight, then put that money into buying the vegetables you already know you should be eating and maybe a gym membership, a pair of running shoes, or whatever equipment will enable you to start exercising, using whichever method of exercise you prefer, regardless of what your genes might tell you to do.

      However, if you have an ancestry test done and discover an unexpected heritage, please don’t start identifying yourself as a hyphenated American, as American is already divided too much as it is. And be sure you know what the service you choose will do with your genetic sample after they are done with it.




23 and Me.

DNA Diet.

DNA Fit.

Fitness Genes.








BuzzFeed. I Tried A Diet And Fitness Plan Based On My DNA And Couldn’t Believe The Results.

Self. I Used DNA Testing To Personalize My Workouts And Here’s What Happened.



Health. Can a DNA Test Really Pinpoint Your Perfect Diet and Workout? Here’s What Science Says.

Healthline. Can Your DNA Determine the Best Diet for You?

New York Post. The ‘DNA diet’ could be a game-changer for losing weight.

NBC News. Trying to Find a Healthy Diet? Look to Your Genes.

Nutritious Life. The Truth About DNA-Based Diets.

Shape. Ask the Diet Doctor: Is the DNA Diet Bogus?

Live Science. Why You Probably Shouldn’t Waste Your Money on DNA-Based Diets.


Miscellaneous: Surgery for Prostate Cancer.

CNN. Angelina Jolie undergoes double mastectomy.

Elite Fitness. Muscle Fiber Types and Training.


Genetic Diets and Fitness Plans: Are They Ready for Prime Time? Copyright 2019 By Gary F. Zeolla.

Creationist Diet: Second Edition; A Comprehensive Guide to Bible and Science Based Nutrition - This Second Edition is 2-1/2 times as long and presents a different perspective on diet than the First Edition. The First Edition mostly advocated a vegan diet, while this Second Edition also advocates for a diet that includes animal foods. But, and this is very important, those animal foods are to be what are called “old-fashioned” meats, dairy, and eggs, not the “factory farm” products that most people eat. What is meant by these two terms and the incredible difference between them is explained in this book. In addition, this book covers a wide range of diet related topics to help the reader to understand how to live a healthier lifestyle according to God’s design.

The above article was posted on this website June 1, 2019.

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