“I know what to do, so why don’t I do it?”

It is one of the most common sentences in nutrition: “I know what to do, I just don’t do it.” It is usually said with frustration, as if the problem is a lack of discipline. In most cases, it is not.

The gap is normal

Eating is not just a decision about nutrients. It happens in the middle of work, family, fatigue, celebration and stress. Knowledge sits in the calm part of your day; many food decisions happen in the rushed part. Expecting knowledge alone to carry you through a hard evening sets you up to feel like you have failed.

Stress, tiredness and evening eating

When you have eaten little during the day and arrive home tired, the urge to eat quickly and eat a lot is a physical response as much as an emotional one. Food can also be how we unwind or reward ourselves. Neither makes you weak. Both are patterns you can plan around.

Rules that backfire

Strict rules (“no carbs after 3”, “no sweets this week”) tend to create an all-or-nothing cycle: one slip becomes “I’ve blown it”, and the rest of the day follows. Research on intuitive eating suggests that approaches focused on internal cues and flexibility are associated with better psychological wellbeing and less disordered eating.

Habits take time

A well-known study of habit formation found it took a median of 66 days for a new behaviour to become automatic – with a wide range between people – and that missing a single day did not undo progress. Imperfect days are part of building a habit, not proof that it isn’t working.

A seven-day experiment

• Pick one point in the day where things usually unravel.
• Plan one small change that makes the next choice easier – a snack in your bag, a simple dinner you can make tired, a glass of water before you open the fridge.
• Repeat it for seven days, noticing what helps rather than marking pass or fail.

Steady is a skill. Like any skill, it grows with practice, especially on the days that don’t go to plan.