What does it mean to be evidence-based?
A Serious Inquiry
Fitness coaches proudly claim they’re “evidence-based”, but what does that mean?
In my view, the term “evidence-based” is typically mishandled and misinterpreted to give those who invoke the phrase a sense of legitimacy. This idea that I am accurate about my claims because I claim to be an evidence-based coach.
Besides the apparent problem with the implication of the phrase, it is still regularly used in the online health space. But again, what does the phrase mean?
The meaning of the phrase “evidence-based” should be self-explanatory, the evocation of the phrase by the person in question means the person bases their knowledge, practice, and advice on ‘evidence’.
Evidence typically refers to scientific peer-reviewed empirical research related to the given topic in question, whether that be nutrition, exercise, physical therapy, etc.
However, there are some issues with differentiating what we mean by ‘evidence’, what constitutes ‘good’ or better evidence from others, and what constitutes the invoking of the title “evidence-based”- just because someone calls themselves evidence-based doesn’t mean they actually care, respect, or understand science as an enterprise and the evidence they use.
This focus on evidence above all else for justifying knowing is known in philosophy as evidentialism.
The Ethics of Belief
Philosopher William Kingdon Clifford published an essay dubbed “The Ethics of Belief” in 1877. The main component of his piece was the evidence it is immoral for our beliefs not to be based on sufficient evidence.
Clifford gives us a story for illustration:
A ship owner sells tickets for a transatlantic voyage, but his ship needed significant repairs and was probably not sea-worthy. The repairs would ultimately delay the voyage and cost the ship owner money so he pushes his doubts and reservations concerning the ship aside. The ship sails off according to schedule, but tragically the ship breaks down and passengers die.
According to Clifford, the ship owner is guilty because he has no right to believe the ship was seaworthy given the evidence presented to him. Even if the ship managed to make the voyage the ship owner is still guilty according to Clifford because he believed something on insufficient evidence.
This is known as Clifford’s principle:
“It is wrong always, everywhere, and for anyone to believe anything on insufficient evidence.”
We can see this currently in the health and nutrition space. People who believe vegetables are detrimental to their health based on weak or no scientific evidence. Others who think certain exercises will “ruin their gains” based again on weak or no scientific evidence.
These beliefs are based on insufficient evidence. But what describes sufficient versus insufficient evidence?
Quality Versus Poor Evidence
“Bad vs. Good”, “Sufficient vs. Insufficient”, and “Quality vs. Poor Evidence” are phrases that essentially get at the same point. We want to separate our idea of good quality accurate evidence from evidence that is bad poor inaccurate evidence.
We can call this the demarcation of evidence.
What do we define as “good” evidence?
Obviously, a scientific study that adheres to quality and ethical research practices would weight more highly than a poorly conducted unethical study.
But what about historical accounts, primary documents, testimonials and other forms of ‘evidence’ outside of science?
This would ential the definition of evidence itself. We can define evidence in terms of the kind of thing which can make a difference to what one is justified in believing.
I would argue justification is inherently important to the concept of evidence as many other evidentialist would. The scientific study that adheres to the best practices of that field of inquiry would more strongly justify a belief that study supports than lets say a persons personal opinion.
Personal opinions are more subjugated to biases, human fallibility, and are unsystematic. The evidence of personal opinion would thus be ranked lower than a scientific study.
This isn’t to say every single study within science is perfect or represents the totality of knowledge about a given topic.
Nevertheless, quality evidence whether science or not would have to make a difference to what one is justified in believing more so than not.
What differentiates “quality” evidence from other forms of evidence that we wouldn’t consider “quality” is the adherence to the best practices within that field of inquiry. In scientific fields this means compliance with ethical standards, conducting established good methodological practices, appropriate statistical or other mathematical calculations, and suitable discemination of that work.
In addition, the realization the evidence in question needs to be in context with the broader scope of knowledge within that field.
This simply means one piece of evidence is insufficient for resting ones justification for belief. There needs to be numerous forms of evidence which are deemed “quality” that point to a particular conclusion, practice, or direction.
Having multiple pieces of quality evidence on a given topic can be deemed sufficient for justifying a belief.
Hume’s Advice
Empiricist philosopher David Hume explains how to form beliefs in light of evidence with the quote:
“A wise man proportions his belief to the evidence.”
This means we need to have our confidence behind beliefs based on the amount of evidence we have for that belief.
For example, if we have numerous scientist within a particular field all conducting research that comes to a similar conclusion, such as human activity (such as burning fossil fuels) has lead to increases temperatures on Earth’s surface and oceans, our confidence behind that belief should be high.
Now if one or two scientist disagree with the majority, produce questionable scientific papers, and have vested interest in fossil fuel industries. The confidence for that belief that human activities are not connected to climate change will be lower.
Our confidence behind our beliefs about something should be in proportion to the evidence.
Therefore, if people online claim a meat only diet is optimal, but just depend on anecdote and poorly constructed survey data our confidence behind that belief should be low.
Multiple pieces of quality evidence would greatly increase our conviction behind a belief.
Being Evidence-Based
I could get into the philosophical debate concerning evidentialism, but for pragmatic reasons we need to define evidence-based in the fitness and health space.
When it comes to health and the multiple domains within health we can define being “evidence-based” under three different considerations from evidentialism:
Beliefs about health should be based on sufficient evidence.
Having multiple pieces of quality evidence on a given topic can be deemed sufficient evidence.
Our confidence behind our beliefs about health should be in proportion to the evidence we have.
These are the three considerations for being an “evidence-based” practitioner in the health space.