Is being obese in our genes?

I often see posts on social media saying that ‘obesity is a choice’ and it really frustrates me. It’s a massive oversimplification of what obesity is. This blog post is going to hopefully clear up whether obesity is a choice, or whether it’s out of our control.

What is obesity? 

I think it’s only fair that I start by laying out what obesity is.

Obesity is when someone has excess fat on their body. It’s clinically defined as a Body Mass Index, (or BMI), of 30kg/m2 or higher. BMI is a ratio of someone’s weight for their height.

person standing on scales

Obesity in the UK has steadily increased over the years, and now over a quarter of adults are obese. If you include people with an overweight BMI, then almost two thirds of adults in England have excess weight. Children living with obesity has also risen, with almost a quarter of children being overweight by age 11.

I do want to point out that BMI is not without its flaws. 

For example, it doesn’t take into account how much of someone’s body weight is fat verses muscle. But it’s a quick way to categorise people. I’ve got a blog post that goes more into BMI here.

So, we know that obesity rates are rising.

We know that the majority of adults are overweight or obese.

But how did we get here?

What causes obesity? 

Obesity is a complex disease. 

Yes, that’s right, obesity is classed as a disease. It's a chronic condition in which excess body fat leads to a host of metabolic and psychological consequences. It’s not as simple as ‘eat less, move more’ as people often say it is.

The causes of obesity are a combination of things, and it’s not as clear cut as we’re led to believe.

Our genetics: 

Our genes, or our DNA, can play a role in the likelihood of becoming overweight or obese. The body is very complex and there are lots of different factors that regular body weight and appetite.

DNA double helix

There are a few ways that our genes can increase the risk of obesity but I’m going to focus on the most common one which is called polygenic obesity.

This means there’s lots of genes that have a negative variation in them, and the combined effect of these genes can contribute to someone developing obesity. 

Our genes could be compared to an instruction manual, and this manual tells our body how to make proteins. These proteins then have roles in the body and perform certain functions.

One of the proteins that can be affected by mutations in genes is called brain derived neurotropic factor, or BDNF. If something goes wrong with BDNF it can lead to an increased appetite which can lead to an increased food intake, which leads weight gain, which leads to obesity.

There are lots of other genes involved in the creation of fat tissue and the control of our appetites. If any of these genes have a small error, then it can mean we’re more likely to have a larger appetite or not feel as satisfied after eating.

This can all lead to excess weight.

person eating a bowl of salad

Of course, we don’t get to control our genes. We’re born with them. But it doesn’t mean that having faulty genes means we’re destined to be obese. Our environment plays a role too.

Our environment: 

People often ignore the effect our environment has on our weight. Our environment is everything around us, our social situations, the location we live in, and our lifestyles.

It’s often said that we now live in an obesogenic environment. This means an environment that supports weight gain and being obese. The obesogenic environment does this by encouraging less physical activity and a higher energy intake.

This could be things like:

  • Having poor public transport and walking routes, so the only option is to drive
  • Having a high concentration of takeaways and fast food restaurants in certain areas
  • Foods high in fat, sugar, and salt being promoted or placed on offer in supermarkets
  • Food delivery apps like Uber Eats and Deliveroo making buying food easier than ever
  • A lack of green spaces and parks for people to exercise in

a park with a bench

One thing these examples all have in common is that they’re out of our control.

  • If someone is having financial difficulties, it makes more sense to buy that foods that are on offer, even if they’re high in fat and sugar.
  • If someone can’t get to work due to a lack of safe pedestrian routes, or unreliable public transport links then they have to drive.
  • If someone has had a long day at work and they want to buy a quick dinner, but their only local options are kebab or fried chicken shops then that’s what they’ll buy.

Yes, all of these examples are still choices that people make. But when these are all the options available, what other choice could be made?

This obesogenic environment contributes to obesity as everything around us is geared for convenience. We don’t have to exert ourselves too much and we have food that is high in energy, cheap, and readily available.

This leads to us ‘eating more, moving less’ which means we have excess energy that is then stored as fat.

All of this doesn’t even consider other factors that can impact on our weight like certain medications, lack of sleep, and stress.

a man yawning

When looking at how genes and environment cause obesity, some people explain it by saying that genetics load the gun, and our environment pulls the trigger. This is quite a graphic way to describe the relationship between them, but it shows the point quite well.

Our genes tell us what we’re more susceptible to, and our environment determines how much it will affect us.

I also often see people trying to do things to speed up their metabolism in order to reduce their weight. But one thing they don’t tell you, is that your metabolism is partly genetic.

Is a fast metabolism the cure to obesity? 

Your metabolism is all the reactions that happen in your body to keep it functioning. These reactions use up energy when they occur. And our bodies are constantly working, even when we’re asleep.

People often try to increase their metabolism, as if their body needs more energy to perform the reactions, it can use up our stored fat. Which can lead to weight loss. If your metabolism is slower then you’ll use up less energy, and more will be stored as fat.

a person measuring their waist

Your metabolism is controlled by your genes, but also things like your lifestyle and age. So, some people may have a naturally fast metabolism due to their genetic makeup. And it can have an impact on their weight but it’s not the be all and end all.

And if someone has a fast metabolism it doesn’t mean they can eat whatever they want. Yes, they can eat lots of ‘junk’ foods and may not gain weight as easily. But the nutritional content of the food we eat still has an effect on our body.

Maintaining a healthy balanced diet is key, no matter what type of metabolism we have. This can help reduce of certain diseases like cancer or type 2 diabetes.

If your metabolism is on the slower side, a way to increase it is to do more exercise. Strength training in particular can be useful. Muscle is very active and uses up more energy even when at rest.

If you’re not a regular exerciser, starting small with 10 minutes of activity a day is a good way to ease yourself in.

a barbell

As you can see, obesity isn’t as simple as eat less, move more. It’s controlled by a web of factors with some being out of your control. Yes, there are some choices we make than can contribute to weight gain. But we have to acknowledge it’s becoming increasingly difficult in our current environment.

Key points: 

  • Obesity is a complex disease, described as a BMI of >30kg/m2
  • Genetics play a role in developing obesity, which we have no control over
  • Our environment also plays a role in in developing obesity. We often can’t change some parts of our environment.
  • Our metabolism is controlled by genetics and our lifestyle.
  • Someone with a naturally fast metabolism may be less likely to gain weight, but it doesn’t mean their diet is healthy.
  • One way to increase your metabolism is to do more resistance exercise.

I hope this post gave you some food for thought.

Bye for now 👋



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