I can see how this might work. For example on a 'slow carb diet' a can of diet soda per day is permitted. It has no sugar and people may consider it a treat - i

I can see how this might work. For example on a 'slow carb diet' a can of diet soda per day is permitted. It has no sugar and people may consider it a treat - i.e. it's better to have that and stave off cravings than to have a chocolate bar.