I really enjoyed the piece in last week’s Guardian pricking the balloon of the ‘clean eating’ movement whose proponents claim that modern life is killing us. I can get quite grumpy about happy-clappy pseudoscience and how it inveigles its way into everyday life. My local coffee shop proudly presents its ‘gluten-free’ brownies, even though the vast majority of people who think they are gluten intolerant simply aren’t. I asked for one with gluten recently and the poor guy behind the counter looked utterly confused.

But the really disturbing part of the article is the author’s anecdote of sharing a stage alongside a qualified dietician and one of the beautiful young champions of the clean eating movement. Whenever either of the first two questioned some of the claims made in the best-selling books of the latter, the audience got aggressive, and they were mocked later on social media. How dare these two criticise something we’ve invested emotional capital in using mere facts?

Another clean eating guru saw the light when her hair started falling out, and ‘fessed up online that her dietary advice was wrong/downright dangerous. While many were understandably angry at being duped, others remained in denial ‘accusing her of being a “fat piece of lard” who didn’t have the discipline to be truly “clean”’.

What all this illustrates is that humans usually make decisions through gut instinct rather than thinking things through. While gut instinct works pretty well for certain decisions – “do I trust this guy?” – it is terrible for others, eg “do I trust climate science?”

‘Confirmation bias’ means that, once we have made our decision, we will cherry-pick the evidence that supports it, and ignore the evidence that doesn’t. No-one is immune to this, although we can train ourselves to fact-check critical pieces of information before acting on them (I am constantly surprised at how many famous quotations are attributed to two or three different historical figures when I do a quick Google).

So, if we want to engage disengaged people in Sustainability, bombarding them with facts just won’t work against the power of gut instinct. So what does?

Experience does.

I went from armchair activist to Sustainability crusader when I saw ecological devastation in the far north of Russia (I could taste the sulphuric acid in the air). My local Nestlé factory loaned electric cars to employees to give them experience of owning one before making a (subsidised) buying decision. I like to involve my client’s employees in generating Sustainability solutions, because that experience makes them much more interested in the subject and challenges their assumptions.

When it comes to food, I have to say, my gut instinct couldn’t be more different than that of the clean eaters. No marketing phrase works better on me than ‘dirty burger’, but I don’t even pretend that it is good for me!