The idea that gut microbes manipulate food choices draws exclusively on rodent studies. Not only do they not demonstrate changes in food preferences, but rely on observations made when species of bacteria are introduced into germ-free animals. This isn’t going to occur in humans, and the trillions of bacteria have massively complex interactions that are not at all understood, quite apart from being unique to each individual.
Even worse is that interventions said to ‘prove’ this theory have been made in uncontrolled conditions. This means results produced are coming from the placebo response – and everything about eating and appetite is susceptible to this well-known phenomenon.
Binge Eating Disorder is well known to be remarkably responsive to placebo, as are appetite hormones. The placebo response is created automatically through expectation, and it makes good sense that appetite hormones respond to expectation. The problem is that the placebo response does tend to be temporary.
This is not to suggest that as the difficulty with overeating is all about mental attitude, you can just snap out of it. It’s not easy to change the way you think in real and meaningful ways, but no matter what intervention you engage in, if you don’t bring your attitudes and expectations along with it, you can certainly run into trouble.
The question is whether it’s best for us to set out to change our hormones or our expectations – the latter being exactly what my work addresses.