In the image above, we have what is known as the "hierarchy of evidence". Those of us interested in the science of exercise, nutrition and health tend to abide by this when making decisions about what is most likely to be true (or least likely to be false).

In the past decade, the evidence-based medicine model has spilled over into the fitness industry, which has had some very positive effects. However, it is now somewhat trendy to be "evidence-based". As a result, it's sexy to throw around studies, as it makes you look pretty damn smart.

This is where things fall apart...

I can probably find you a paper to support virtually any stance. If you are not scientifically literate, it's very difficult for you to decide whether or not the evidence is actually up to scratch for me to be able to hold that stance. 

The reality is that you will ALWAYS have people who just want to prove their point, even if it comes at the expense of the truth. But, you can most definitely improve your critical thinking skills and upgrade your bullshit detector, by simply understanding what the hierarchy of evidence looks like. 

So, the next time somebody throws a study at you, you could ask them "what type of study is this?". When they answer, you can check out where that study design lies on the hierarchy of evidence. If they can't answer you, then you can be very confident that they don't really understand science, haven't read the study and don't know what they are talking about.

Is it as simple as just knowing the hierarchy of evidence? 

Absolutely not.

There are multiple layers that one must peel back when assessing the quality of evidence. For example, someone may have sent you a randomised controlled trial, but that doesn't mean that it's necessarily very strong evidence. There may have been no blinding of the participants or researchers, a high dropout rate, questionable statistical methods and so on. 

"Science" is not a black and white thing. The message here is that just because someone throws studies around does not mean they are doing so with the knowledge of the quality of the evidence. One paper also means very little, as it is the wider body of evidence that is most likely to bring us closer to the truth.

The type of study may vary in its strength based on the type of question too, as some research questions may limit you from doing a randomised controlled trial. For example, it would be fairly unethical to run a trial in which you told one group to smoke and the other to avoid smoking, wouldn't it? In those cases, we rely on other study designs, even though a randomised controlled trial is stronger on paper.

Don't fall into the trap of those with an agenda by believing anyone who throws around studies, and always maintain a degree of uncertainty. The scientific method allows us to reduce uncertainty over time, but you shouldn't ever feel like everything is black and white.

Kind Regards,