This is what the NHS website says.
"Within a healthy, balanced diet, a man needs around 10,500kJ (2,500kcal) a day to maintain his weight. For a woman, that figure is around 8,400kJ (2,000kcal) a day.
These values can vary depending on age, metabolism and levels of physical activity, among other things."
People will look at that and think they can have 2000 calories a day, more if they exercise a lot. But that isn't the case.
Shouldn't it say around 1500 calories (for women) but varies with age, activity levels etc? That way people will eat up to 2000 calories when doing exercise not when sat on their arse?
2000/2500 is taught at a young age but the "this varies depending on exercise" bit isn't! I teach maths and one of the exam papers even has a task where you work out what 1 third of your 2000 calories is and pick meal from a fast food menu to "fit in with your recommended calories". 
I just think it would help with the obesity levels to re-educate people and this is probably a good place to start.