When you walk into Hungry Jacks, or McDonalds, or Kentucky Fried Chicken, and order your Whopper Value Meal, Big Mac Value Meal, or Ultimate Burger Meal, what does 1430kj, 2590kj and 3800kj (approx.) mean to you? Probably not very much.
But, instead of esoteric energy counts, what if you were confronted with something more comprehensible, like 75 minutes of sprinting (Medium Whopper Value Meal), or a 2 hour game of squash (Large Big Mac Value Meal), or, perhaps 5 hours of fast swimming (Ultimate Burger Meal)? Would you think again about buying all that food?
I think you would.