Do Our Genes Impact Our Jean Size?



Can our genes actually affect our weight loss efforts?


The short answer is - Yes, they can! Genes play a really important part in many outcomes including body composition, weight loss and exercise outcomes to name a few but they’re not the only thing that matters or determines our faith!

Here is an important equation to understand…


Genes + Environment = Outcome


Think of your genes like the blueprint of your body. We inherit them from our parents. We can’t change the genes we receive from our parents. However, genes may open a door to a particular path but we do not have to follow that path. Our genes are not our destiny. Genes can be influenced by environmental factors including nutrition, smoking, physical and mental stress and other factors like pollution, which can in turn change how they’re expressed and our outcomes.

So what about obesity? Obesity has risen dramatically over the past number of decades. Our genes have not changed, but our environment has which has in turn affected how our genes are expressed. A lot of research has been carried out over the past number of years into obesity. Many genes have been identified which make a person more susceptible to developing obesity. The key word is susceptible. One such gene which has been studied in great detail is the FTO gene. Having this gene variant is associated with increased hunger, decreased satiety, increased caloric intake and overall an increased risk of developing obesity.


Having a gene such as the FTO variation makes a person more likely to become obese, but it is not fatalistic. This risk can be increased or decreased by environmental factors. So you might carry gene variants for obesity which increases your risk of becoming obese, but what you do every day and the lifestyle you live determines your outcome. The same goes for someone who doesn’t carry any gene variants for obesity and is at a very low risk of becoming obese. They can live a healthy lifestyle which will give them greater protection. Or they can live an unhealthy lifestyle and may still develop obesity.


So are environmental factors more important than our genetic make-up in determining our outcome? An interesting study by Turnwald et al (2019) looked at the effect of someone’s beliefs about their genetics in comparison to their actual genetic make-up on their outcomes. In this study, they performed genetic testing on all participants and separated the study group into two groups. Researchers told one group they had ‘bad’ genes for satiety and for aerobic exercise. They told the other group they had ‘good’ or more favourable genes for satiety and aerobic exercise. But here’s the catch. The splitting into groups was done regardless of their actual genes. Each group actually had a mix of people with ‘good’ and ‘bad’ genes.


The results were extremely interesting! Participant’s beliefs about their genetics influenced outcomes more than their actual genetic profile. The group who had been told their genetics predisposed them to poorer cardiovascular outcomes for aerobic exercise actually had poorer outcomes for cardiovascular fitness at the end of the study, whether their genetics actually did give them a less favourable outcome or not. On the other hand, the group who had been told they had favourable genes for cardiovascular fitness saw improvements whether they actually had the favourable gene or not.


Similar results were also seen when they looked at their perceived hunger. The group who were told they had a poor gene for satiety saw increases in perceived hunger, regardless of whether or not they actually had the less favourable gene. The group who were told they had the favourable gene for satiety saw a decrease in perceived hunger, regardless of whether they had the favourable gene or not. This study showed that while genetics do play an important role, environmental factors and what a person believes, is actually more important for outcomes in the case of these genes.


So yes, genes do play a role in obesity. Someone’s genetics can be part of the reason they find it harder to lose weight, struggle to gain muscle or have very levels of hunger. But your genetics are not your faith. The lifestyle you live, how you manage stress, the food you eat and the exercise you do can all confer massive protection against diseases such as obesity, cardiovascular disease and diabetes or it can promote their progression, regardless of your genetic make-up.


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