Scientific Consensus: Most People Don’t Understand It, and That’s Why Everything is a Mess

3 terms you’ll need to recognize for this blog post:

1.) Outlier noun
– One that exists outside or at an extreme of a category, pattern, or expectation; an extreme case or exception. (source: Yahoo Dictionary)

2.) Weight of the evidence noun
the strength, value and believability of evidence presented on a factual issue by one side as compared to evidence introduced by the other side (legal definition)

3.) Scientific consensus noun
– the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity (source: Wikipedia)

Word cloud for Scientific community

I’m occasionally accused of being a ‘hypocrite’ because I promote moderation in diet, and I can also be resolute in my position that fitness and health professionals should base our advice and recommendations on evidence rather than opinion. For instance, recently one guy couldn’t understand why I would promote moderation in diet but then turn around and take a hard line on vaccines. Why am I not moderate in my opinion of vaccines like I’m moderate in my opinion on diet, he wondered?

Here’s the thing about that: I’m not moderate in my opinion on diet. My opinion on diet is based FIRMLY on the evidence. The weight of scientific evidence supports moderation as the MOST EFFECTIVE approach to long term weight management success. Most scientists agree, and most studies support this conclusion. Yeah, there are a few outliers, but like I said, the weight of the evidence supports moderation. When many scientists examine all the evidence and come to the same conclusion based on the weight of the evidence, rather than on the outliers, it’s what is known as scientific consensus. There will always be outliers, but when most of the evidence points to one conclusion, we can be reasonably assured that that conclusion is accurate. For example, scientific consensus has been reached on the topic of the relationship between the sun and the Earth. There is no debate as to whether the Earth revolves around the sun, rather than the sun around the Earth. The weight of the evidence supports the conclusion that the Earth revolves around the sun, and the vast majority of scientists agree – this is called scientific consensus.

I base my opinions on both diet and vaccines (and many other topics) on the weight of the evidence. And I’m not moderate at all in my opinion that fitness and health professionals should absolutely base their recommendations on the evidence. Not on their opinions. Not on guesses. Not on their experience. Not on their gut feelings. Not on ‘what just feels right’. Credible research. Scientific consensus. Evidence. I will discuss why at the end of this post.

A recent thread on my facebook wall regarding Google’s new proposed ranking algorithm was really enlightening for me. I suddenly recognized a big contributor to the anti-science movement, as many of the arguments used in this thread were exactly like those used in arguments made to promote anti-science rhetoric on other topics, like vaccines, GMOs, climate change and the like. But seeing them applied to a different topic than I’m used to brought the issue into better focus: lots of people really don’t understand the concept of scientific consensus. For the record, I don’t think the people making these arguments are regular readers of my page, as my regular readers have demonstrated a pretty high level of scientific literacy. I think these are people who perhaps saw my post on a friend’s timeline and this post was their first visit to my page. I’m going to synopsize the main arguments made, and explain why they’re flawed. You’ll see that these are all variations on a general theme, with nuanced differences:

1.) I don’t want scientists/doctors making decisions for me and my family! Scientists and doctors can be biased. I know what’s best for my family.

Indeed scientists can be biased, that’s why instead of drawing recommendations from one scientist, we look to the general consensus among lots of different scientists. Drawing from many different sources reduces the influence of bias. The more scientists, and the greater the level of consensus, the less chance that bias is influencing the recommendations. As far as knowing what’s best for one’s family, this isn’t always true, unfortunately. Most of us do not have the knowledge and experience level of a scientist or doctor, and have not learned how to critically evaluate scientific evidence. We are more likely than a trained scientist to confuse correlation with causation or fall victim to other forms of faulty logic. Unless you are a doctor, you really don’t know more about medicine – or physiology, or immunology, or disease – than your doctor.

2.) We can’t trust that science knows what is truth. Science has been wrong before! Just look at the recent reversal on cholesterol! And they used to believe the earth was flat!

Indeed, scientific knowledge is ever-evolving, as we make new discoveries and learn more about the world around us. This is science’s STRENGTH, not it’s weakness. Science is the exploration and examination of evidence, and we are continually gathering new evidence. Again, this is a reason to look to the evidence, and the scientific community, as a whole, and not focus on any single study or scientist. As for the cholesterol reversal, people are confusing policy with science. What we are observing is a policy reversal, not a scientific consensus reversal. There was not a strong scientific consensus that dietary cholesterol contributed to high blood cholesterol, policy was based on weak evidence. And it was never scientists that believed the Earth was flat, it was a cultural belief. It was early explorers and astronomers that proved it was round, as they experimented to determine if their hypothesis was correct. It was cultural belief that held the earth was flat, and scientific inquiry that showed it was round.

3.) How can we ever know anything is true? For every study that shows one thing, there’s another that shows the opposite! And for every scientist that makes one claim, there’s another scientist that makes the opposite claim!

Actually this isn’t true for most scientific theories for which there is general scientific consensus, such as vaccines, GMOs, climate change, evolution, the Earth’s rotation around the sun, etc. In all those cases, most scientists, and most studies, support the same conclusion. And a few outlying studies and rogue scientists make other claims. The problem is that our media tends to give equal air time to both ‘sides’ of the ‘debate’,  giving the impression that the debate is equally weighted (or that there is a debate at all), when in reality, the VAST majority of science and scientists agree and only a small handful make outlying claims. The reality is, that for most of these topics, there are hundreds or even thousands of studies that support the generally accepted conclusion, with a small small handful of studies making an outlying claim (or even only one, like the SINGLE rat study that gets trotted out over and over and over as ‘evidence’ for sugar addiction). It is not one for one by any stretch of the imagination.

4.) What if new evidence emerges? Do scientists expect us to bury our heads and just accept their word and never question consensus?

Actually, no. The scientists themselves question consensus. That’s what science is. The questioning of our understanding, they search for new information, the examination of new and old evidence. Consensus is reached when evidence becomes undeniably compelling, but it is never set in stone. Science would revise it’s stance on the earth’s relationship with the sun if compelling new evidence emerged to challenge our current understanding. That is the very nature of science. It is the opposite of blind faith. It is the eternal pursuit of truth. You’re thinking of emotional investment in a belief, ie ‘faith‘, when you talk of burying your head and never questioning an assertion. Not science.

5.) Science doesn’t have all the answers.

No, indeed. Science doesn’t have all the answers. Science DOES have more – and better – answers than guessing does, though.

You can tell from a lot of these arguments that people really just don’t understand what scientific consensus is. That they don’t understand the difference between fact and opinion. That they don’t know how to tell good science from bad science, and don’t know what outliers are. It’s not their fault – these things aren’t always taught in school, and logic isn’t natural to our human brains. Once we’ve formed a belief, we have a hard time changing it even when confronted with evidence that it’s not true. Our perceptions are influenced by our subconscious prejudices. We look for patterns and aren’t good at telling correlation from causation. These are skills that require training and practice.

Now, I mentioned that I’d discuss why I hold firmly that we, as fitness and health professionals, are obligated to act and provide recommendations based on evidence rather than opinion. It is exactly because humans are so bad at the things I just mentioned. Because our opinions may be flawed, informed by emotion rather than fact. Because we may be mistaking correlation with causation. And when we give advice from these flawed sets of beliefs, we are in essence guessing, and it is irresponsible to give people health advice based on guesses. Because it could affect their health and even their lives. It could kill them if we are wrong. And we are more likely to be wrong if we are basing our advice on anything other than scientific consensus based on the weight of the evidence.

We owe the people who come to us for help the respect of basing our advice on facts and evidence, not on our own opinions and (potentially flawed) perceptions. Basing our advice on our opinions is profoundly egotistical and self centered.

What if you are wrong?

My recommendations are firmly evidence based because I am not so arrogant as to believe I know better than the entire scientific community.

And I am critical of so many in the fitness, fad diet and alternative health industries because they ARE so arrogant as to believe they know better than the entire scientific community, and their opinion-based (and frequently magical-thinking based) recommendations put their clients’ health – and lives – in danger.