I'm sure that most of us would have heard or said this at some point "I'm unable to get healthy due to my genetics" or "I can't lose weight because it runs in my family". On the other side, people say "You can't lose weight because nobody runs in your family!"
All jokes aside, let's talk about an interesting idea. What matters more in your pursuit of health - is it genetics which is what you are born with that is hereditary, and could be linked to your DNA or is it the environment - your diet, workout routines, people with who you hang out?
It is the classic question of nature vs nurture.
When talking about health, I want to focus on chronic diseases. You'd think that genes are the all-important factor that influences your health, but it is just a starting point. However, we have seen that there have been multiple studies that indicate it's a combination of both these factors.
Apart from the addictive tendencies and risk factors for health, genetics could even impact traits like height, weight, grit, extroversion etc.
Let's talk about height. It's unlikely that the gene pool has changed all that dramatically in just a few generations. Instead, the most powerful height boosters have been nutrition, clean air and water, and modern medicine. (Incidentally, generational gains in weight have been even more dramatic, and again, that seems to be the consequence of eating more and moving around less rather than changes in our DNA.) Even within a generation, you can see the influence of the environment on height. Children who are provided healthy food in abundance will grow up taller, whereas malnourishment stunts growth.
Likewise, traits like honesty and generosity and grit, are genetically influenced and, in addition, influenced by experience, Ditto for IQ, extroversion, enjoying the great outdoors, having a sweet tooth, the likelihood that you'll end up a chain smoker, your risk of getting skin cancer, and really any other trait you can think of. Nature matters, and so does nurture.
Maybe the question isn't what matters more, but how do they both matter collectively? The concept of Epigenetics comes into place here which talks about how environmental influence affects the expression of genes.
Interaction between genetics and environment
Human health is highly dependent on genetics, yet it is also known to be affected by factors in an individual’s environment – and these days that environment is quite stressful. As we shelter in place amid the coronavirus pandemic, anxiety combined with changes in our routines is driving a significant increase in alcohol consumption, and some are experiencing weight gain. On top of all this, due to recent wildfires and air pollution, the air in many areas is filled with smoke and hazardous particulate matter.
Long before the events of 2020, scientists were trying to unravel the details of how the separate influences of inheritance and surroundings push and pull against one another to govern traits – such as height, athletic ability, and addictive behaviour – and disease risk.
Few diseases result from a change in a single gene or even multiple genes. Instead, most diseases are complex and stem from an interaction between your genes and your environment. Factors in your environment can range from chemicals in air or water pollution, mould, pesticides, diet choices, or grooming products.
Subtle differences in one person’s genes can cause them to respond differently to the same environmental exposure as another person. As a result, some people may develop a disease after being exposed to something in the environment while others may not.
Although this interaction influences so many problems, let's talk about two important ones - weight gain and brain diseases.
Weight gain
Heritability is a term used to define the estimated proportion of a phenotype – the observable characteristics of a trait – that can be explained by genes alone. Past research has shown that there is a large variation in the heritability of body weight: for some individuals, genes appear to account for about 25% of the predisposition to be overweight, while for others, the proportion can be as high as 80%. Many scientists believe that susceptibility genes make some people more prone to weight gain and that environmental factors – including those occurring in utero – trigger the expression of genes that cause weight gain.
Paul Williams, a statistician at Lawrence Berkeley National Laboratory (Berkeley Lab), specializes in investigating the instances where genetics and environment are most closely intertwined. His work focuses on a phenomenon called “quantile-dependent expressivity,” wherein the genes that predispose people to certain traits are amplified by environmental factors.
After examining Framingham data – including measurements of visceral and subcutaneous fat using CT scans, which are more precise than simple body mass index (BMI) numbers – Williams found that weight heritability was over three times greater in offspring who were at the 90th percentile of the body weight distribution than those who were at the 10th percentile.
He said the results are consistent with previous research by others showing that obesity genes have a bigger effect on people in certain lifestyle categories: heavy consumers of fried food, sugar-sweetened beverages, and fatty foods; heavy television watchers; heavy eaters; meal skippers; those who are sedentary; and those who are stressed or depressed.
Williams hopes that this new analysis, recently published in the International Journal of Obesity, will encourage scientists to move toward a new paradigm in studying and treating obesity.
“Different genes and different environmental effects are sometimes interpreted as separate, one-off phenomena, but I think these results suggest that everything is much more interconnected – namely, that seemingly separate factors can all act to increase body weight, and as body weight increases so do the effects of any obesity genes that a person carries,” he said.
Brain diseases
This is one of those parameters which we often think are fixed - it's the genetics but the studies show otherwise. One such disease is Alzheimer's.
The dietary concept may be surprising because most of the popular press today treats Alzheimer's as a genetic disease. They say it's your genes, rather than your lifestyle choices, that determine whether or not you'll succumb. However, when you examine the distribution of Alzheimer's disease around the world, that argument begins to crumble.
The rates of Alzheimer's vary tenfold around the world, even taking into account that some populations live longer than others.[1] For example, in rural Pennsylvania, if you knew one hundred senior citizens, an average of nineteen of them would likely develop Alzheimer's disease within the next decade. However, that number would probably be closer to just three out of one hundred if you lived in rural Ballabgarh, India.[2] How do we know some populations aren't just more genetically susceptible? Because of migration studies, in which disease rates within the same ethnic group are compared between their current locale and their homeland. For example, the Alzheimer's rates among Japanese men living in the United States are significantly higher than those of Japanese men living in Japan.[3] The Alzheimer's rates among Africans in Nigeria are up to four times lower than those of African Americans in Indianapolis.
This indicates the impact of the environment (especially diet) on predicting the risk of brain diseases.
Other studies
A study of twins conducted by Stanford University School of Medicine investigators shows that our environment, more than our heredity, plays the starring role in determining the state of our immune system, the body’s primary defence against disease. This is especially true as we age, the study indicates.[4]
The emerging consensus is that genetic and environmental risks usually multiply together in a mathematically straightforward way. And when it comes to the genes vs. environment debate, most of the time it’s both.[5]
Conclusion
When I think about what affects our health and the risk of chronic health issues, this quote by Isaac Newton comes to mind (also used repeatedly in one of my favourite TV shows Dark):
“What we know is a drop, what we don't know is an ocean.”
We need more thorough research on this question, but until then it is safe to say that genes are not something in our hands. It's the card that you are dealt with and you can't do much about it. What you can control are your environment and your habits. So the incentive is to work towards your lifestyle and keep improving that.
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