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.Ridley, 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.Costill, 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.Myerson, 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 ...