‘Nature vs. Nurture’, the debate that has been with us for years, has reared its head again.  So, the question on everybody’s lips is “can our environment be blamed for obesity or are some people really born to be fat?”  David Geffen, of UCLA, recently published findings that suggest the latter (Red Orbit, 2013).  After a two-year study, Geffen concluded that obesity is less about what you put in your mouth and more about your DNA, meaning that maybe your genes really are making you fat.  But is he right? 


In 2007, New Scientist reported a University of Oxford study which showed that around half of the 39,000 people tested had a defective FTO gene (Roxanne Khamsi, 2007).  This defect made them 30% more likely to be obese.  Moreover, 16% of those tested were found to have a double defect, or the defective gene twice, leading to a massive 70% chance of developing obesity.  These are startling statistics, especially given the high regularity of the defective gene.  What’s more, this study isn’t alone in supporting nature’s side of the debate. 

Timothy Frayling of the University of Exeter examined further research, when he declared that the link between obesity and genetics is stronger than we might think (Timothy Frayling, 2012).  Frayling looked into adiposity rates in twins (the rate in which they store fat) and found an extraordinarily high correlation.  Similarly, he compared BMI levels of adoptive children to both their adoptive and their biological parents.  The biological association was significantly stronger than the adoptive one, suggesting that nurture has less to do with obesity than nature.  In fact, Frayling concluded that around 60-70% of weight gain is related genetics rather than environment.  With findings like these, it is easy to blame nature for your spare tyre. 

External Factors

However, some of these results could be a little misleading.  For example, the figures in the first study are certainly impressive but those found to have the double defective FTO gene were typically only three kilograms heavier than those without.  Although not good news, a three kilogram weight gain could hardly be to blame for the rising trend in morbid obesity.  Similarly, Professor John Wilding claims that whilst genetic defects can cause untold weight gain (such as a leptin deficiency), these disorders are extremely rare and cannot account for the majority of obesity cases.  In fact, Wilding states that the human genome hasn’t changed for approximately 50 years, whereas the obesity epidemic didn’t truly start until the early 1980s (John Wilding, 2012).  In other words, we can’t blame genetics alone. 

Thus, environmental factors must play their part.  It is undeniable that in Western countries, increasingly sedentary lifestyles and cheaper ‘junk’ food have an effect.  But perhaps genetics still play a role.  Rather than making us fat, perhaps our genes are to blame for the way in which our bodies react to external factors, which in turn make us gain weight.  To illustrate this point, Frayling makes an analogy between eating and smoking (Timothy Frayling, 2012).  Imagine everyone inhaled the same amount of smoke every day.  Although the cause would be consistent, the consequence wouldn’t – some would develop disease as a result, whereas others would see little or no affect.  This is because genetic susceptibility to smoke differs among people – how you are affected depends on how your body reacts.  The same can be said of food: how your body reacts to environmental factors is all down to your personal genetic make-up. 

Genetics and External Factors

This takes us back to Geffen’s 2013 findings (Red Orbit, 2013).  Geffen and his team in UCLA have discovered certain genes that affect the way in which our bodies react to fats and sugars.  They took different strains of mice and placed them in varying environmental conditions (in order to properly reflect the diversity of human society).  The change in fat cells was then measured over a two year period.  During the initial four-weeks, almost all the mice gained weight.  This increase then stopped, suggesting that there is a set point when fat cells will stop reproducing and this is down to genetics.  Geffen argues that his research demonstrates that dietary responses, such as fat cell reproduction and metabolic rate, are highly influenced by genetic factors.  Thus, obesity could be a mix of the way we eat, societal changes, and our DNA. 

The Truth

Whilst all this may be true, we can’t get away from the fact that our lives are more sedentary now.  Today, work is less about toiling the land and more about sitting in a stuffy office using a computer all day.  Grabbing a bit of lunch is less about sandwiches with some fruit and more about convenience foods that are high in additives, sugars, and saturated fats.  So the answer to the question “are your genes really making you fat” is yes, there is a chance that they are.  Is that the end of the issue though?  No, it most definitely is not. 

Ultimately, we must take responsibility for our own bodies.  It may well be the case that person A puts on weight easier than person B, and yes, that could be caused by genetics.  It may well be the case that your body will hold on to fat cells for longer and reproduce them faster than your neighbour’s body does and that could also be a result of your genetics.  But we can’t just give up on our health.  As a society, we need to stop finding excuses for our obesity epidemic and we need to start taking action to resolve it.  We need to accept that even if our genes have given us a ‘bum deal’ and made it harder for us, we can still do it – we can still be fit, healthy, and ready for anything. 


British Medical Association, 2013.  Doctors Demand Broader Approach to Tackling Obesity [online] Available at: <bma.org.uk/news-views-analysis/news/2013/January/doctors-demand-broader-approach-to-tackling-obesity/> [accessed 23rd May 2013]

John Wilding, 2012.  Art The Causes of Obesity Primarily Environmental? Yes.  [online] available at: <www.bmj.com/content/345/bmj.e5843> [accessed 25th May 2013]

Red Orbit, 2013.  Is Obesity Genetic? [online] Available at: <redorbit.com/news/health/1112760879/is-obesity-genetic-010913/> [accessed 23rd May 2013]

Red Orbit, 2012.  Is it Our Genes or the Environment that Cause Obesity? [online] Available at: <redorbit.com/news/health/1112692729/is-it-our-genes-our-the-environment-that-causes-obesity/> [accessed 23rd May 2013]

Roxanne Khamsi, 2007.  Hunt for Obesity Gene Yields a New Suspect [online] available at: <www.newscientist.com/article/dn11592> [accessed 23rd May 2013]

Timothy Frayling, 2012.  Are The Causes of Obesity Primarily Environmental? No.  [online] available at: <www.bmj.com/content/345/bmj.e5844> [accessed 25th May 2013]

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“IT’S NOT MY FAULT! IT’S IN MY DNA!” ARE YOUR GENES REALLY MAKING YOU FAT? by UrbanSculpt Staff Writer Victoria Froud is licensed under a Creative Commons Attribution-NoDerivs 4.0 International License.