Genetics and Obesity: Who Is to Blame?


It’s no secret that there is an obesity epidemic happening right now in countries across the globe. Even in historically poor or malnourished nations, obesity is rearing its ugly head and causing problems. It affects the poor as well as the rich; the strong and the weak. As it is a severe global issue, people toss blame around a lot, and some of it has landed at the feet of genetics. So today we’re going to look at genetics and obesity.

Some suggest that it is human variations in DNA that cause people to become overweight. This is technically true. A little bit. Unfortunately, the issue is not so simple, and the interactions between genetics and obesity are varied and complex.

However, the better we understand the genetic influences on obesity, the easier it will be to counteract against them. The human genome is almost unfathomably long and complicated, and there are many points in our genetic code that can influence if we become overweight and how.

It is not accurate to say that obesity is wholly determined by hereditary factors, but it is equally erroneous to say that everyone has the same opportunities to be physically fit and that it’s all in your head. With that in mind, let’s look at some of the ways that your genetics can determine your risk of obesity.

What Are Genetics and Obesity

In the simplest of terms, obesity means being overweight and having too much fat stored in your body. So much so that it begins to be detrimental to your health. It is the result of an energy imbalance; your body takes in more energy than it uses and stores the rest as fat. But there are other factors at work. The rate at which your body converts food into energy is not consistent.

It is dependent upon your level of physical activity as well as a slew of hormones that regulate your body function which can be. The production and reception of these hormones are often in flux and can be suppressed.

How much you eat is also dependent upon your body’s physiological functions. Hormones regulate when you feel full or when you feel hungry, and these are also susceptible to change. Being overweight is caused by overeating, but how much you eat and how much is “enough” varies significantly from person to person. That’s where genetics and obesity come in.

Genetics and Obesity: Single Gene Forms of Obesity

Single gene, or monogenic, causes of obesity are rare, but they do exist. This is as close as it gets to the “genetic scapegoat.” A single mutation can cause disorders that affect hormone production and reception. These hormonal disorders often involve leptin, a hormone that regulates energy production and appetite.

Persons with these disorders have little control over their weight gain, as their bodies simply resist burning fat and creating energy. These disorders can cause severe weight gain, but once diagnosed they can be treated and the weight gain reversed with appropriate medication and alterations to habits.

There are also several disorders such as Prader–Willi and Bardet-Biedl syndromes which are chromosomal abnormalities. These syndromes list obesity alongside many other problems such as mental retardation or reproductive issues. These syndromes are severe, yet rare.

In fact, all of these monogenic syndromes and disorders are scarce. So scarce are they, that it is not possible to attribute them as causes of the growing obesity epidemic. Humans have become demonstrably overweight in recent decades in comparison to generations past, which points to the reasons being in lifestyle and diet choices. Still, these factors do not affect everyone equally.

Genetics and Obesity: Multiple Gene Forms of Obesity

Also called “Common Obesity,” this form of obesity is caused by a variety of mutations working in tandem. Together, they do not cause weight gain, but they do cause a person to have a genetic predisposition to being overweight.

Some people react differently to outside stimuli or specific kinds of food intake, and this can lead to excessive weight gain above the average amount experienced by other persons in the same socioeconomic or geopolitical category. Put into layman terms, this means that a cheeseburger might fill someone up while leaving another hungry; one person burns fried foods quickly into energy and another does not.

However, there is no one “obesity gene” that we can point to as the culprit. It isn’t a switch we can flip. Polygenic mutations mean that influences from many different gene sites cause these predispositions, which are equally numerous and varied.

Common obesity can cause the accumulation of excess body fat in a several different ways. Usually, a change in energy production and regulation is at fault. Appetite regulation is also a frequent contributor to weight that can be affected by specific genetic factors. Ironically, these genetic mutations helped humans to survive when food sources were rare and unreliable. But in today’s plentiful society, these genes are a detriment. So technically, yes, genes can contribute to obesity. However, there is a big but attached to that statement (pun intended).

Products of Environment

Polygenic factors can contribute to obesity, but they do not cause them. Whether or not you become obese is still largely reliant on your environment. The genetic factors associated with “common obesity” are reliant on the food you eat and the activity you perform. A giant plate of french fries will make most people fat; some will just get heavier faster. Exercise will help you lose weight, but some people may require more activity than others.

So, despite genetic contributors to being overweight, the right environment can keep the vast majority of people at a healthy weight. Not only are genetic risk factors not the only culprit for weight gain, but we also are still not sure to what extent they affect weight gain. Most studies done to determine the genetic causes of obesity have so far been unable to be replicated. What does this mean? Well, it tells us we know that genes are not the sole cause of the obesity epidemic, and we aren’t even sure how much they contribute to getting fat. The number of genes at work is vast and difficult to study let alone identify.

How Do We Know It’s Because of Our Environment?

It is comforting to think that genetics are to blame for us being overweight; it takes the blame off of us. But the evidence does not back that up. Multiple studies have been done on twins, siblings and other groups of family members to compare their BMIs. Identical twins, even ones separated at birth, most often had roughly the same BMIs. The similarities increased the closer the pairs were related (non-identical twins, brother and sister, father and son, etc.). Their BMIs were similar, but not identical.

Data from these studies may suggest that those who are related have similar body types because of their shared DNA, but consider the fact that family members often have similar lifestyles. Environmental factors such as diet, physical activity and others have apparent effects on a person’s weight. Where they were and what they did is more important than who they are and what’s in their DNA. The data also varies from study to study, meaning we cannot definitively say if genetics are a primary cause of obesity. The evidence suggests it is not.

In Summary

So, what does all of this mean for the average person? All of this genetic mumbo-jumbo is all well and good, but what does that mean for me? The implications of this data and these studies are both positive and negative.

The Bad News

Bad news first. There is no evidence to suggest that genetics play a key role in the development of obesity. They contribute but aren’t the deciding factor. We also can’t single out a mutation and lay blame at its feet. There are some cases of monogenic causes of obesity, but these are exceptions that often come with much more severe complications.

There will likely never be a gene therapy or pill that you can take to stave off obesity miraculously; it just isn’t that simple. There are so many different mutations and genetic variations at play causing “common obesity,” and we understand very few of them well. We may yet unlock the code of genetic predisposition to obesity, but this will not help us cure the disease, only understand it. Knowledge is power, however, and we cannot fight obesity without it. Environmental factors are more important than our genes in determining if we gain weight, but learning which genes do what will help us adjust our environments accordingly.

The Good News

As bleak as this sounds, this is actually great news. You are not destined to be overweight, despite what your DNA says. Your habits, lifestyle, diet and choices have a much higher impact on your weight than anything else. You are in control, and not at the mercy of fate.

Eating right, exercising more and altering your lifestyle are difficult things to do to be sure; difficult but not impossible. Rewriting our genetic code is what’s (currently) impossible, so we are fortunate that is not the answer to losing weight. We are overweight because of the choices we make and the environment we live in, but neither of those things are set in stone.

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