All-or-nothing thinking

All-or-nothing thinking is a thinking trap in which there are only two states: perfectly on track or a complete failure. In cognitive behavioural therapy, it's one of the best-known cognitive distortions. When you're trying to lose weight, it sounds like this: “I had an ice cream today, so the day is ruined.” “I missed my workout, so I can write off the week.” “Either I do the diet one hundred per cent, or I give up on it completely.”

What happens next was shown by the psychologist Peter Herman in an experiment back in 1975: people on a diet who first had to drink a milkshake went on to eat more ice cream than those who hadn't had one – as if the day was a write-off anyway. For people not on a diet, it was the other way round. Herman and his colleague Janet Polivy later called this the what-the-hell effect. So the strict rule creates exactly the behaviour it is meant to prevent. If you think in percentages, you carry on eating normally after the ice cream; if you think in black and white, you're more likely to finish the whole tub.

The way out is to think in shades of grey. A day with 80% good decisions is a good day. A week with two workouts instead of three is a week with two workouts, not zero. A helpful question is: “What would be the next smallest good decision?” – a glass of water, a walk, vegetables with dinner. You don't have to rescue the whole day, just the next step.

Language gives the trap away too: “always”, “never”, “everything”, “ruined”, “forbidden”. If you hear words like these in your head, you can consciously rephrase them: “mostly”, “rarely”, “this time”. For families: there are no forbidden foods, only everyday foods and sometimes foods. Children who grow up with strict bans learn exactly this black-and-white thinking – and then often eat the forbidden foods all the more as soon as they're allowed to, or in secret.