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Why Are Doctors Moving Away From Body Mass Index? A Biological Psychology Podcast Episode.

Updated: Aug 1, 2023

Why Are Doctors Moving Away From Body Mass Index? A Biological Psychology and Health Psychology Podcast Episode.

For decades, doctors have used the Body Mass Index (BMI) to determine if someone is at a healthy weight. This is one of the factors used in clinical psychology to diagnose eating disorders and any people involved in clinical work uses the BMI from time to time. Yet the BMI’s usefulness has been criticised and extensively questioned in recent years because of its failures. Therefore, in this health psychology podcast episode, we focus on why doctors are now moving away from BMI and what could be used in the future. If you enjoy health psychology, clinical psychology and biological psychology, you’re going to love today’s episode.

This podcast episode has been sponsored by Biological Psychology. Available from all major eBook retailers and you can order the paperback and hardback copies from Amazon, your local bookstore and local library, if you request it. Also, you can buy the eBook directly from me at

Why Are Doctors Moving Away From BMI?

Personally, this doesn’t surprise me that this is happening within the medical field. Since if you’ve done clinical psychology before, this is a subset of arguments that I learn about recently. There were a lot of problems with the BMI, and we will talk about these, but I do welcome the vote by the American Medical Association to move away from the BMI.

In addition, in case you’re new to Body Mass Index, this is the formula where a person’s weight in Kilograms is divided by the square of their height in metres. Then the result of this formula is classified into one of four categories. They are:

· Underweight

· Normal weight

· Overweight

· Obese

These labels aren’t rare in the US medical system, and as someone from the UK, I regularly hear these labels too.

However, what is really interesting is the history behind the BMI because once you know the history of this formula then you really start to question why on Earth it’s used in medicine in the first place. It isn’t based on evidence at all.

What Is The History of The BMI?

The weird thing about the BMI is that it was invented in the 1830s by a Belgian statistician because they wanted to describe the “average man”. I suppose that is fine fair enough because we all want to research and describe things from time to time.

Nonetheless, it rose to popularity in the medical field during the 1970s by the physiologist Ancel Keys. Since he was looking for a better way for the US health insurance companies to estimate a person’s body fat. The theory behind this is that there is a correlation between someone’s body fat and the risk of them dying.

In other words, he wanted to make it more effective for US health insurance to charge people more money if they had more body fat.

Now as someone from the UK, and I don’t doubt the US health insurance companies will sadly move into this country in my lifetime. I think this is awful, crazy and harsh, because I have only ever heard of horror stories from Americans about their insurance companies.

Anyway, the BMI was a much better and simpler calculation for finding out someone’s body fat compared to the methods used by the US health insurance companies at the time.

Furthermore, to be fair, we have to admit that the BMI is very useful at evaluating large populations, but it is a lot less helpful for evaluating a single person’s health. The reason for this is because there is no way at all to quantify a person’s muscle and bone mass so athletes tend to have higher BMIs because of their higher muscle mass. Yet according to the BMI, they might be overweight.

Another example is that as a person ages, they lose muscle mass and increase abdominal fat and this unhealthy change isn’t picked up by the BMI.

A third problem is that the BMI was mainly developed as well as tested on white men. Yet a person’s body composition varies massively between genders, ethnicities and races. For example, a perfectly healthy black woman might appear to be overweight or even obese according to the BMI.

This is why the BMI is a rather useless metric if we really look into it.

Tomiyama et al. (2016)

Whilst there are a lot of studies that investigate the sheer amount of people that are miscategorised by the BMI, I do want to focus on this particular study. Due to this particular one actually compared the BMI against other measures of health. Including, blood pressure, insulin resistance, glucose, cholesterol and a few others in over 40,000 adults.

The results demonstrated nearly half of the “overweight” people as well as 30% of the “obese” people actually had healthy metabolism.

Moreover, more than 30% of the people with a so-called normal weight had an unhealthy metabolism. Therefore, if you take this number and apply it to the US population then this means that there are over 74 million people in the US that are misclassified as unhealthy or healthy according to the BMI.

As a result, whilst the BMI isn’t perfect and I believe it has very, very limited uses, the American Medical Association doesn’t want to resign it to history. Instead they want doctors to use other factors to determine someone’s health like those used in the study above. And this is a very good quote from American Medical Association Immediate Past President Dr Jack Resneck:

“There are numerous concerns with the way BMI has been used to measure body fat and diagnose obesity, yet some physicians find it to be a helpful measure in certain scenarios. It is important for physicians to understand the benefits and limitations of using BMI in clinical settings to determine the best care for their patients.”

Health Psychology Conclusion

At the end of this podcast episode, I have to admit that I really am going through a biological psychology phase at the moment for a reason I flat out don’t understand. Yet I wanted to do this podcast episode because I heard about the disadvantages of the BMI but I haven’t looked into them in any depth until now.

I understand why the BMI isn’t a great tool and I really hope that medical doctors do start to walk away from the BMI properly.

And to bring this back to psychology, as much as I hate this, I truly, truly hate this. Since the American Psychological Association has a lot of medical input, the BMI requirements for a lot of eating disorders will not be replaced with something more useful to psychologists until the medical doctors get rid of it themselves.

This is another reason why we need to move beyond diagnosis like I’ve done previous podcast episodes on.

Anyway, until that happens, we will have to put with the BMI for a little bit longer and we can start to slowly use other measures of body fat in the meantime.

But this is certainly a step in the right direction.

I really hope you enjoyed today’s biological psychology podcast episode.

If you want to learn more, please check out:

Biological Psychology. Available from all major eBook retailers and you can order the paperback and hardback copies from Amazon, your local bookstore and local library, if you request it. Also, you can buy the eBook directly from me at

Have a great day.

Health Psychology References

Caleyachetty, R., Meunnig, P., & Kengne, A. P. (2016). Misclassification of cardiometabolic health when using body mass index categories. International Journal of Obesity, 40(8), 1332-1332.

Goh, K. C., Safonov, M. G., & Papavassilopoulos, G. P. (1994, December). A global optimization approach for the BMI problem. In Proceedings of 1994 33rd IEEE Conference on Decision and Control (Vol. 3, pp. 2009-2014). IEEE.

Rothman, K. J. (2008). BMI-related errors in the measurement of obesity. International journal of obesity, 32(3), S56-S59.

Tomiyama, A. J., Hunger, J. M., Nguyen-Cuu, J., & Wells, C. (2016). Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005–2012. International journal of obesity, 40(5), 883-886.

Why Doctors Are Moving Away from BMI | Psychology Today

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