Does obesity really cause heart disease?

It’s funny what people chose to put their faith in. Very few of us trust politicians or lawyers. We are taught not to believe everything we read and are sceptical of the media. But most of us have no problems trusting in science.

In fact, very few people question health professionals and the studies that determine their guidelines and policies. We assume they have our best interests at heart and know exactly what they are talking about. But why? Why are scientists any more trustworthy than politicians?

A lot of the research that medical experts quote are funded by drug companies. In fact, lots of those experts work for said drug companies in some form or other. So just because they say something is true, doesn’t necessarily mean it is.

Photo by Edward Jenner

Let’s take obesity. How many people here think that obesity causes heart disease?

Most of you? Well, that’s not surprising. I mean, unless you live under a rock, this fact has been impressed upon you for the last few decades. Just look at the headlines. We are in the middle of an obesity epidemic. Obesity is set to become the world’s biggest killer.

And guess what?

It simply isn’t true.

Say that again?

Woah. I can already hear the critics shouting out in protest. I know what you are thinking. Surprise, surprise, the fat doctor doesn’t believe that obesity causes heart disease. How convenient.

[Oooh, burn]

But chill critics, chill. I never said that obesity doesn’t cause heart disease. I just said that we don’t know that it does. And yes, there is a really big difference.

Here’s what we do know. If you take a group of people with heart disease, a significantly higher proportion of them will be obese. Also, if you were to follow a group of obese people over the course of the next 10 years, significantly more of them will develop heart disease than non-obese people.

Obesity is without a doubt a risk factor for heart disease. But that doesn’t mean that it causes heart disease.

Risk factor is not the same as cause

Let’s look at a completely unrelated analogy. There are a disproportionately higher percentage of black men in the prison system in the USA. One out of every three black boys born in the US today can expect to be imprisoned at some point during their lifetimes as opposed to only one in seventeen white boys.

There is no question that being black is a risk factor for incarceration in America. But does that mean that being black causes people to be criminals?

Just to be clear, the answer is NO!!!

[If you disagree, then feel free to remove your racist self from my presence.]

There are a number of complex reasons why black men are more likely to be imprisoned than white men. But it is ridiculous to assume that the colour of your skin will somehow predetermine whether or not you are destined to commit a crime.

Photo by Luis Araujo 

In the same way, obesity has a number of underlying causes. Many of them are modifiable and without a doubt the two most important ones are physical inactivity and poor diet. Oddly enough, lack of physical activity and poor diet are both risk factors for heart disease, no matter how much you weigh.

So is obesity itself the cause of heart disease, or is it the underlying factors that cause your arteries to fur up and get blocked over time?

Does it really matter?

The reason I am so keen to find out the answer is because I believe it fundamentally changes the way that we should be treating obesity. Both as individuals and as a society as a whole.

Right now, our focus is always on weight loss. A person comes to see the doctor and we measure their weight and height. We calculate their BMI and determine that they are obese. We tell them that this puts them at risk of heart disease, diabetes, arthritis, cancer and a whole host of medical conditions.

So far, so good. The evidence is there and it is pretty hard to argue with.

So what do we do next? In a nutshell, we tell people to eat less and exercise more. Ideally in a compassionate way and in slightly more detail. Still, this is all good stuff. We are tackling the modifiable risk factors in a hope that our patients can make some positive improvements to their health.

It’s what happens next, that I have a problem with. And anyone who has been there knows what is coming. We bring you back sometime later and we weigh you. If you’ve lost a lot of weight, we give you a big pat on the back and tell you to keep up the good work. If you’ve lost a bit of weight, we encourage you to try harder. And if you haven’t lost any weight, we secretly judge you!

[That last part was meant to be a joke, by the way. But in reality health professionals are well known to be fat phobic and that’s a topic for another time.]

From that moment onward, we have set a precedent. We are not really interested in whether or not you have started exercising and changed the way you eat. We are interested in whether or not you have lost weight. Weight loss becomes the primary focus, irrespective of any of the positive changes you may have made.

It is important to interpret the numbers correctly

“What’s the difference?” I hear you cry.

The difference is that some people make relatively minor changes to their diet and lose a significant amount of weight. Others make some pretty radical changes, but the weight takes a lot longer to shift. And this is pretty demoralising. After a while, dieting becomes more problematic and we can end up becoming our own worst enemies.

I plan on writing more about this in future posts, so I won’t dwell on that last statement for now. But I think it is very important that we clear up a very simple fact once and for all. Nobody knows for sure if obesity is actually bad for you. In fact, there are a number of studies that demonstrate that obesity actually extends your life expectancy once you have been diagnosed with certain conditions. Including heart disease. It is called the obesity paradox.

In addition, the rates of obesity have doubled in some parts of the world over the last 50 years. And yet the rates of diabetes and heart disease have remained approximately the same. (In fact, the prevalence of diabetes has gone up a little but this may be due to the fact that we have stricter diagnostic criteria than we used to).

Photo by E A Unuabona

If obesity inevitably leads to diabetes and heart disease like we are lead to believe, then why hasn’t the prevalence of these conditions drastically increased? Because not all obese people are going to end up with diabetes or dying of a heart attack. In the same way that not every smoker is going to end up with lung cancer.

[Smokers are 30 times more likely to die of lung cancer than non smokers. But the majority of smokers will not die of lung cancer. This once again show that risk is not the same as cause.]

The problem with trials

Heart disease is by far the biggest cause of death in the UK. As I said already, we know that people who are diagnosed with heart disease are more likely to be obese. But we still do not know that obesity itself causes the heart disease.

In order for us to know for sure, we would need to take a large group of people ( a few thousand to be on the safe side) from an early age (ideally childhood) and separate them into two groups. One group would need to become obese and spend the rest of their lives this way.  The other group would have to stay within a normal healthy weight range for the rest of their lives. 

Then we would follow them up for the next 60 years or so and record whether or not they were diagnosed with heart disease.  If more people in the obese group died of heart disease than in the non-obese group (and assuming this was a statistically significant result), we would have proven that obesity causes heart disease.

We call this a randomised controlled trial and this is only real way we can prove that one thing causes another without introducing a whole bunch of bias and speculation in to the mix. 

When the best just isn’t possible

Can anyone see a potential problem with the design of this trial?! Since it would be pretty unethical and impossible to organise, we need to look to the next best thing.

Now you could just take a group of young people and separate them into two groups according tho their weight. Then follow them over the next forty years and see how many of them develop heart disease. But the problem with this type of trial is that people were not randomly assigned to each group which means you have automatically introduced bias.

They may have already picked up bad eating habits or live sedentary lives. They may have other factors that have predisposed them to obesity. So how will you ever know whether it was the obesity itself rather than these predisposing factors or pre-determined habits that caused the heart disease?

Photo by Kaboompics .com 

You could also take a large group of people who have already been diagnosed with heart disease and measure their weight and BMI. This is by far the simplest way to collect data but it also the most inaccurate. There are a number of studies that show statistically significant correlations between two completely unrelated things.

For example, there is evidence to show that people whose initials spell out something negative (such as P.I.G or B.A.D) have a significantly shorter life expectancy than those with positive ones (like W.I.N or T.O.P). True story.

Do we need to stop weighing people?

So this ended up being a lot more science than I had first intended, but I just wanted to make the point that the science behind obesity is not exactly what you think it is. Obesity may be the cause of a number of conditions such as heart disease. It may be set to become the leading cause of death in the UK.

But we do not know this for sure. An alternative theory is that obesity is caused by a number of underlying risks factors and it is these risk factors themselves that are also responsible for heart disease. And if that is the case, I believe we need to be treating the root cause of the problem as opposed to the symptom itself.

Photo by Allgo

Rather than focusing on weight loss, we could encourage people to make healthier choices that are independent of the number on the scales. We could find other ways to measure progress as opposed to tracking BMI. In short, we could stop weighing people all the time.

And imagine just how liberating that could be.

Did I just blow your mind? Did I make you mad? Do you disagree with everything that I have just said? Than why not leave a comment below? And if you’d like to know more about me, including how to subscribe to my mailing list then click here.

2 thoughts on “Does obesity really cause heart disease?”

  1. Fascinating stuff. You did not make me mad at all. You made me think and question things, which is always a very good thing. I think that placing the emphasis on weight also means that people who make poor choices for their health but remain within ‘normal’ BMI think they will automatically be OK. I think you are right and that being as active and healthy as we can is the thing we should all be aiming for regardless of what the scales tell us. Always a great read on a Tuesday morning!

  2. Pingback: Five things I love about my belly - The Fat Doctor

Leave a Comment

Your email address will not be published. Required fields are marked *