September 19, 2019

Shannon Miller

Genetic Testing (Part 2): Will it Ever Live Up to the Hype?

Heather Huntsman, Ph.D., CSCS, follows up on her last guest blog on consumer genetic testing to discuss how close science is getting to using DNA to make informed health decisions around diet and exercise. While we’re moving in the right direction, it’s more complicated than we think.

In a recent blog post we discussed some of the limitations of direct-to-consumer genetic testing. As intriguing as some of their claims are, and as much as we want to believe them, the promise of precision health is still a distant reality. The truth is that most of our traits are incredibly complex and are a result of many genes expressed at varying levels. Then to complicate things even further, our ancestry (or genetic background), and the environment have a huge impact on this already complicated equation.1,2

A great example of this complexity was recently published in the Journal of the American Medical Association.3 In this year-long study individuals were assigned to either a low-carbohydrate or low-fat diet. Genes associated with carb or fat metabolism were assessed ,as well as weight loss. At the end of the study scientists compared the genetic profiles of those with genes predictive of more carb vs. more fat metabolic sensitivity to the successful weight loss in their randomly assigned diets. The answer-the number one predictor of diet success was adherence. Those that did the work saw the results. Surprisingly there was no association between having the “right genes” and being assigned to the “right diet.” I want to emphasize here that we know with 100% certainty that the genes that were tested are important in metabolism. That said, this study highlights how complex the process of weight loss is, and that the basics are, well, basic for a reason.

Diet, exercise, and sports performance are all examples of complex traits that involve several systems (e.g. cardiovascular, muscular, and metabolic function), and arguably hundreds if not thousands of genes are involved.1,2 While that can be an overwhelming thought, I do want to leave you with some promising updates. Even though genetics are complicated, we are getting closer to answers every day. So, stay curious and stay tuned. The evidence is growing for genes like ACE and ACTN3 that may be predictive of a genetic edge in endurance or power sports depending on which version you have. Now, that isn’t to say that we will ever be at a point where we can predict athletic success, but I do think potential talent identification is in the realm of possibility.4

Also, the genetic data we have is improving. Since we first sequenced the human genome in 2003, the majority of genetic information collected has come from people of European decent. Unfortunately, that limits the associations we can make, especially when you do not have European lineage (refer to the previous blog post about the contribution of ancestry). This has led to several efforts from leading scientific institutions to recruit and include underrepresented groups so we can improve our understanding. In a 2016 article published in Nature, data coming from non-Europeans has grown by over 4-fold in the past 7 years.5

So, we still aren’t there yet, but we are moving in the right direction. There will be a day where we can all use our genetic information to make more informed health and treatment decisions. But until that day comes, keep working hard, be mindful of what you eat, and use data from resting metabolic rate and body composition tests to make sure you are staying on track for a healthier version of you.


  1. MacArthur DG, North KN. (2005) Genes and human elite performance. Human Genetics 116(5):331-339.
  2. Puthucheary Z, Skipworth JRA, Rawal J, et al. (2011) Genetic influences in sport and physical performance. Sports Medicine 41(10):845-859.
  3. Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association with Genotype Pattern of Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA 319(7):667-679.
  4. Guth LM, Roth SM. (2013) Genetic Influence on Athletic Performance. Current Opinion in Pediatrics 25(6): 653-658.
  5. Popejoy AB, Fullerton SM. (2016) Genomics is failing on diversity. Nature 538(7624):161-164.
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