Genetics, Weight Loss & Personalised Goals

Written by: Kyle Riley, BSc (hons) Ex Sci, Therapy Co-Founder

Everyone is unique, from the 25,000 genes we possess through to the way those genes express (hair, eyes, skin colour etc.). 

So, why is it that we continue to follow a one size fits all approach in all walks of life?

From following our favourite influencer’s ‘what I eat in a day’ through to images of what a ‘healthy body’ looks like. We are constantly told to search for the holy grail ‘one’ way to eat, move and think, as well as who or what we should aspire to be.

And that message needs to change!

Whenever you approach the conversation of individuality, particularly with regard to genetics. It is often met with disdain as though it is an excuse for ‘hard work’ or a reason to play ‘victim’. And of course, blaming genetics for every woe in life is not the healthiest way to approach things, there is not a lot you can do about the cards you have been handed from your parents. So whilst I agree that you need to focus on what you can control, it is also important to understand that completely disregarding the role genetics play can also leave you vulnerable to following the next guru’s instagram caption telling you that ‘you can be just like me if you work hard enough’. As it is this ‘advice’ that actually leaves many people following information that is either completely wrong for them, or has them comparing their journey to that of another’s in an unhealthy way, often causing more stress, self-loathing and creating the opposite of ‘personal empowerment’. 

‘Genetics is an excuse – Your weight/how you look is purely down to how hard you work!’

This is a common post I see flooding social media channels from fitness influencers, telling their followers that they way they look is purely down to how hard they work and that genetics has nothing to do with it. And again, whilst I understand the sentiment in trying to get people to focus on the things they can control, that message is not entirely true. 

In fact, research shows the heritability of weight is around 70%. Meaning 70% of the difference in people’s weight throughout a population are due to inherited DNA differences (1,3). 

And with the growth in precision medicine and personalised health, there are many studies in nutrition, exercise, behaviour change and more now validating what genetic research has been showing for some time. That in any given intervention, there are those who ’respond’ and those who do ‘not respond’ and some of these differences in response can be attributed to differences in our DNA. This directly opposes the idea that ‘it all comes down to hard work’, in fact, it means there are people who can actually work at the same effort, or harder than others and actually achieve ‘worse’ results!

As an example, one particular study looked at overfeeding pairs of identical twins (putting them in the same calorie surplus) over a 100 day period to assess the variance in weight gain and fat deposition. The results of the study shown that identical twins (who share the same DNA) put on similar amounts of weight during the overfeeding period. But when comparing the weight gain between different pairs of twins (comparing those with different DNA), some put on only 4kg’s of additional weight, whilst others added up to 13kg’s of additional weight, all whilst following the same caloric surplus/overfeeding strategy! The results of the study concluded that the similarity in weight gain between pairs of twins and the differences when compared to other twin pairs is likely due to genetic factors (2).


And it’s not like we haven’t noticed this difference play out in our everyday lives! This is precisely why you can start a 12 week challenge with your best friend, follow the exact same exercise and nutrition program, and even though you both swore blind you followed the protocol to the best of your ability, you still have completely different results at the end.

Is DNA Our Destiny?

So, does this mean our health is predetermined? And that if we have a genetic propensity to higher weight, that there is nothing we can do about it?

Absolutely not!

Weight is not 100% heritable and still allows for environmental influence in how those genes express (cue epigenetics). Meaning we can still change our energy intake through food choices, increase our energy expenditure through exercise and activities of daily living and therefore manage our weight.

But what this DOES show us is that genetic differences influence how our body composition journey may look in comparison to someone else, and even if I put every single member of Therapy on the exact same exercise and nutrition program, I would see a completely different response in terms of:

  • Rate of fat loss loss (how quickly a person loses body fat)
  • Body fat distribution (where we store fat) 
  • Body fat utilisation (the areas we lose fat from easier/hold on to more) 
  • Rate of muscle gain (how quickly we build muscle)
  • Muscle shape (whilst we can build size and strength, the shape of our muscles has a large genetic influence)
  • Body Anthropometry (Whilst we can control our composition, we cant change the length of our limbs, ratios and proportions, which influence how we look)

And I haven’t even started on things like appetite regulation, willpower and the behavioural genetics side of things! 

Taking Responsibility

Is it victimhood then, to suggest that Genetics play a role in our differences and that the reason we do not all look alike is due to factors outside of our control? 

No, it paints a realistic picture and expectation that every single person is different, that we are meant to look different and many of these differences are controlled by our genes. 

And it is from that position I believe people can truly take ultimate responsibility for their lives, by having the complete picture, by understanding the strengths that lie in our differences, by setting realistic goals, expectations and choosing to take positive steps towards improving whatever aspect of health it might be with an understanding that the journey will look different from people online, friends and fellow sweat buddies in the gym. 

So, the next time you find yourself negatively comparing the way your body looks to someone else, just remember that you have a completely different body, with a completely different set of genes and environmental circumstances. And regardless of the nutrition program they are following, the exercise plan they do, it is unlikely that your body will respond in the same way that there’s will, and that is OK. 

Instead, the secret is for you to define your personal vision of greatness, see your body for the incredible strengths it possesses and set personalised goals as to what a happy, healthy version of YOUR UNIQUE BODY looks like. 


  1. Stunkard AJ, Foch TT, Hrubec Z. A twin study of human obesity. JAMA 1986;256(1):51–54. Search PubMed
  3. Knock et al., Behavioural Genetics 7th Edition