Remember when everyone gave up smoking when they learned it was unhealthy?
Remember when everyone put down the burgers when they found red meat / carbohydrates / fat / salt / etc… was unhealthy?
Remember when all the alcohol companies went bust when it was announced alcohol is a toxin?
We understand, on a personal level, that facts don’t really matter to our decisions. Broadly they do of course. We wear a coat when it rains. We drive at the speed limit (mostly…). We follow rules. Yet we still smoke. We eat burgers. We drink to excess. We do bad things because they feel good.
If you want people to stop doing something make that something feel bad.
Telling people eating burgers is bad for their health is marginally effective. Telling people eating a burger is morally wrong and they will be judged for it is highly effective.
This taps into social proof and, more importantly, feels bad. You feel guilty. You feel ashamed. And you stop doing it.
Similarly if you want people to eat healthily make eating healthy feel good. This is the premise behind the highly successful Food Dudes program at Bangor University which teaches kids to feel good about eating healthily.
I have a theory that this is why so many people who eat restrictive diets become fanatical about it. By creating an almost religious fervour around something you are more likely to follow through.
So. To summarise. Changing behaviour is all about making people feel differently.