Tracking your kilojoules doesn’t have to be an exercise in perfection.

According to research from the University of Pittsburgh, a diet-and-exercise log can work even if you fill it out less than two-thirds of the time. People who kept a weight-loss diary (on paper or with an app) at least 60% of the time for a year – and as little as 30% of the time the next year – kept weight off.

If you’re 
diligent in the beginning, you start to keep track mentally, making the journal less necessary, says study author 
Dr Lora Burke.