DNA Is Not Destiny: The Truth About Fitness Genetics

You’ve been hitting the gym regularly, maintaining a balanced diet, and following all the best advice from your favorite health gurus, but you’re not quite seeing the results you’ve expected. Have you ever thought, “Is it just my genes?” Have you ever told someone else that your current state of health is just genetic?

If so, you’re certainly not alone. I heard it all the time when I worked on-on-one with clients as a personal trainer.

Many people question why they can’t bulk up or slim down as quickly as their friends or why some people can eat all they want without gaining a pound. Is it truly down to genes, or is there more to it?

In this article, I will guide you through the complex interplay between our DNA and our fitness levels. By the end of this read, you’ll have a newfound understanding of why we are the way we are and, more importantly, what you can do about it.

Together, we’ll explore fascinating scientific research and dive into topics like how genes can influence physical traits relevant to fitness, the impact of genetics on how our bodies respond to exercise, and the never-ending “nature vs. nurture” debate.

Genetics and Fitness 101

You might’ve breezed through high school biology, nodding along when the teacher mentioned DNA, genes, and chromosomes. But let’s face it, back then, you probably didn’t imagine you’d be revisiting the topic in the context of your gym routine. So, let’s roll up our sleeves and demystify the relationship between your genetics and fitness.

The Basics of Genetics

First things first: What exactly is genetics? At its core, genetics is the study of genes, the segments of DNA that provide the instructions for making proteins in our bodies. Think of your genes as the blueprint, the original plan that determines everything from your eye color to, yes, certain aspects of your fitness profile.1Ridley, M. (2006). Genome: The Autobiography of a Species in 23 Chapters. Harper Perennial.

Every cell in your body contains DNA, and every DNA molecule comprises two strands that twist together to form a shape we often refer to as the ‘double helix.’ This DNA is broken down into units called genes. Imagine your DNA as a cookbook and genes as individual recipes. They dictate how things should be constructed and function.

How Genetics Can Influence Fitness Levels

Now, the juicy part: how do these genes affect our fitness? Your genes can influence many factors related to your physical capabilities. For example, a study published in the Journal of Applied Physiology found that individuals with certain genetic markers were more predisposed to have a higher percentage of slow-twitch muscle fibers. These fibers are essential for endurance sports like marathon running.2Costill, D. L., Daniels, J., Evans, W., Fink, W., Krahenbuhl, G., & Saltin, B. (1976). Skeletal muscle enzymes and fiber composition in male and female track athletes. Journal of Applied Physiology, 40(2), 149-154.

Conversely, some genetic markers indicate a higher percentage of fast-twitch muscle fibers. If you’ve ever marveled at the explosive power of sprinters or weightlifters, you can bet that fast-twitch muscle fibers play a significant role in their prowess.

Real-life Examples of Genetic Factors Affecting Fitness

To make this even clearer, let’s discuss some real-world examples. Have you heard of the ACE gene? Research published in the European Journal of Applied Physiology points to the fact that individuals with a specific variant of the ACE gene might have an edge in endurance events. On the other hand, a different variant of the same gene is linked to strengths in power and sprint activities.3Myerson, S., Hemingway, H., Budget, R., Martin, J., Humphries, S., & Montgomery, H. (1999). Human angiotensin I-converting enzyme gene and endurance performance. European Journal of Applied Physiology, 80(3), 224-230.

Another interesting gene is ACTN3. This particular gene has been dubbed the “sprint gene” because studies, such as one from the American Journal of Human Genetics, show that those who carry certain variants of this gene excel in short, explosive activities.4Yang, N., MacArthur, D. G., Gulbin, J. P., Hahn, A. G., Beggs, A. H., Easteal, S., & North, K. (2003). ACTN3 genotype is associated with human elite athletic performance. American Journal of Human Genetics, 73(3), 627-631.

But before you rush off to get a genetic test to see if you’re destined to be the next Usain Bolt or a marathon champ, remember: while genetics provides some pieces of the puzzle, it’s not the entire picture.

Genes and Physical Traits

When you gaze in the mirror, ever wonder why your body looks the way it does? It’s not just about the workouts you do or the food you eat. Genes significantly influence our body types, muscle composition, metabolic rates, and even our potential maximum oxygen uptake (VO2 max). Here’s the breakdown:

  1. Body Type: Your genetic code plays a role in determining whether you’re ectomorphic (naturally slender), mesomorphic (naturally muscular), or endomorphic (naturally broader with a higher body fat percentage).5Wang, Z., Heo, M., Lee, R. C., Kotler, D. P., Withers, R. T., & Heymsfield, S. B. (2001). Muscularity in adult humans: proportion of adipose tissue-free body mass as skeletal muscle. American Journal of Human Biology, 13(5), 612-619.
  2. Muscle Fiber Type: As mentioned, genes determine the ratio of slow-twitch to fast-twitch muscle fibers. This distinction is crucial as slow-twitch fibers are more suited for endurance activities, while fast-twitch fibers excel in short, powerful bursts of action.
  3. Metabolic Rate: Your genes can affect your basal metabolic rate (BMR), which is the rate at which your body burns calories when at rest. A study in the International Journal of Obesity revealed certain genetic markers associated with faster BMRs, which might make weight management easier for some.6Speakman, J. R., Rance, K. A., & Johnstone, A. M. (2008). Polymorphisms of the FTO gene are associated with variation in energy intake, but not energy expenditure. International Journal of Obesity, 32(7), 1088-1092.
  4. VO2 Max: Often deemed as the ultimate indicator of cardiovascular fitness, your VO2 max, or the maximum amount of oxygen your body can utilize during intense workouts, is partly dictated by genetics. Research from the Journal of Physiology indicates that up to 50% of the variance in VO2 max among individuals can be attributed to genetic factors.7Bouchard, C., Daw, E. W., Rice, T., Pérusse, L., Gagnon, J., Province, M. A., … & Rao, D. C. (1998). Familial resemblance for VO2max in the sedentary state: the HERITAGE family study. Journal of Applied Physiology, 84(2), 475-479.

Genes and Environment

While your genes lay the foundation, your environment, including your training program, diet, and lifestyle habits, can influence how these genetic traits manifest. For instance, someone genetically predisposed to have a higher VO2 max can still fall short if they lead a sedentary lifestyle. Conversely, dedicated training and optimized nutrition can help someone without the ‘ideal’ genetic makeup to still achieve impressive athletic feats.

The Role of Epigenetics

Beyond just the genes themselves, there’s a rapidly growing field of study called epigenetics. This looks at how environmental factors can switch genes on or off, influencing how they’re expressed. So, while you can’t change your DNA sequence, certain lifestyle factors like nutrition, stress, and exercise can influence how your genes function.8Feil, R., & Fraga, M. F. (2011). Epigenetics and the environment: emerging patterns and implications. Nature Reviews Genetics, 13(2), 97-109.

Beyond Genetics: The Power of Training, Nutrition, and Willpower

Training and Adaptation

Genetics might give you a starting point, but training is the path that can lead you to your pinnacle. The human body is wonderfully adaptive. Even if your genes suggest a predisposition towards endurance, with the right strength training regimen, you can build muscle and power.9Campos, G. E., Luecke, T. J., Wendeln, H. K., Toma, K., Hagerman, F. C., Murray, T. F., … & Staron, R. S. (2002). Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. Journal of Strength and Conditioning Research, 16(4), 525-534. Conversely, if you’re naturally powerful, incorporating cardiovascular workouts can boost your endurance.

Interestinlgy, many years ago, I did a genetics test myself. It showed that I was predisposed to be an endurance athlete, with genetic markers as high for slow-twitch endurance fibers as they’d ever seen. I don’t want to look like an endurance athlete, though. Nor, do I want to train like one. I prefer building as much muscle as I naturally can. So, I have to consistently train against what my genetics would prefer.

Interestingly, a study in the Journal of Strength and Conditioning Research illustrated that, irrespective of genetic makeup, consistent resistance training can stimulate muscle hypertrophy and strength gains. Your body responds to the challenges you set for it, often in remarkable ways.

Nutrition: Fueling Your Potential

You’ve heard it before: “You are what you eat.” And when it comes to maximizing your genetic potential, nutrition is a pivotal player. Consuming a balanced diet rich in protein, healthy fats, some carbohydrates, and micronutrients aids muscle recovery and growth, and boosts overall athletic performance.10Mutch, D. M., Wahli, W., & Williamson, G. (2005). Nutrigenomics and nutrigenetics: the emerging faces of nutrition. European Journal of Clinical Nutrition, 59(S1), S16-S21.

Research in the European Journal of Clinical Nutrition underscores that while genetics can influence how our body processes certain nutrients, our diet can modulate the expression of genes related to metabolism, body weight, and disease risk. So, no matter your genetic hand, playing your nutritional cards right can have a profound impact on your fitness journey.

The Willpower Factor

While genes and environment play their parts, one’s mindset and determination are equally crucial. Numerous anecdotes underscore individuals who, despite not having the ‘perfect’ genetic makeup, achieved remarkable feats through sheer will and relentless training. Your mental fortitude, resilience, and passion can bridge any genetic gaps, propelling you to heights that genes alone might not have predicted.

As captured in a study from Psychological Science, mental grit and determination often play a more significant role in achieving long-term goals than innate talent or genetic predisposition.11Duckworth, A. L., Peterson, C., Matthews, M. D., & Kelly, D. R. (2007). Grit: perseverance and passion for long-term goals. Psychological Science, 18(6), 493-499. It’s a testament to the age-old adage: “Where there’s a will, there’s a way.”

Bridging Genetics and Lifestyle

To make the most of your genetic potential, first, understand it. DNA testing kits, now readily available, can offer insights into your genetic predispositions related to fitness.12Collins, M., Xenophontos, S. L., Cariolou, M. A., Mokone, G. G., Hudson, D. E., & Pitsiladis, Y. P. (2004). The ACE gene and endurance performance during the South African Ironman Triathlons. Medicine & Science in Sports & Exercise, 36(8), 1314-1320. These tests can hint at:

  1. Muscle fiber composition
  2. Injury risk
  3. Optimal workout recovery times
  4. Tendencies toward certain nutrient deficiencies

However, it’s crucial to approach these results with a pinch of salt. While they provide valuable insights, they don’t offer a comprehensive view of your fitness potential. Remember, genetics is just one part of the equation.

Personalizing Your Training

Armed with genetic insights, tailor your training regimen:

  1. For Endurance Predispositions: If you’re genetically inclined towards endurance, incorporate more aerobic activities like long-distance running, swimming, or cycling. But don’t neglect strength training; it can enhance endurance performance by improving muscle efficiency.13Ronnestad, B. R., & Mujika, I. (2014). Optimizing strength training for running and cycling endurance performance: A review. Scandinavian journal of medicine & science in sports, 24(4), 603-612.
  2. For Power and Strength Predispositions: Favor resistance and high-intensity interval training (HIIT) sessions. However, adding occasional endurance workouts can amplify cardiovascular health and stamina.
  3. For Mixed Predispositions: If you have a balance of both, opt for a mixed regimen, blending elements of strength and endurance training.

Adapting Nutrition

Dietary needs can differ based on genetics. Some may have a higher predisposition for vitamin D deficiency, while others might metabolize caffeine faster.14Cornelis, M. C., El-Sohemy, A., Kabagambe, E. K., & Campos, H. (2006). Coffee, CYP1A2 genotype, and risk of myocardial infarction. JAMA, 295(10), 1135-1141. By understanding these tendencies, you can adjust your diet to optimize nutrient intake and energy metabolism. Work with a nutritionist familiar with nutrigenomics to get a diet plan that aligns with your genetic makeup.

Navigating the Limits of Genetics in Fitness

While DNA testing offers fascinating insights, it’s critical not to view these results as definitive scripts for your fitness journey. Relying too heavily on genetic predispositions can lead to a deterministic mindset, possibly demotivating some individuals if they believe they don’t have the ‘right’ genes.15Bray, M. S., Hagberg, J. M., Pérusse, L., Rankinen, T., Roth, S. M., Wolfarth, B., & Bouchard, C. (2009). The human gene map for performance and health-related fitness phenotypes: the 2006–2007 update. Medicine & Science in Sports & Exercise, 41(1), 35-73. Your genes offer potential pathways, not fixed destinies.

Genetics is a complex and rapidly evolving field. While current research provides a foundation, there’s so much we don’t know yet. Many genes interact in ways that are not fully understood, and single gene effects can sometimes be overstated.16Joyner, M. J., & Coyle, E. F. (2008). Endurance exercise performance: the physiology of champions. The Journal of Physiology, 586(1), 35-44. Thus, while genetic insights can be helpful, they should not be the sole determinant in fitness decisions.

Engaging with DNA testing means sharing your genetic information with companies. While many of these companies prioritize user privacy, there are concerns about data security and potential misuse of genetic information.17Hazel, J. W., & Slobogin, C. (2018). Who knows what, and when?: A survey of the privacy policies proffered by U.S. direct-to-consumer genetic testing companies. Cornell Journal of Law and Public Policy, 28(1), 35-66. It’s vital to ensure you’re comfortable with the privacy policies of any DNA testing service you use.

Practical Summary

So, does genetics play a role in your health and fitness? Absolutely. But it’s not as much of a factor as you may wish it were. Your health and fitness are ultimately determined by your choices and your consistency with those choices. You can’t choose your genetics, but you can choose wellness or illness.

Photo by Alexander Redl on Unsplash