The jury is out as to whether or not this chocolate bar really helps you work, rest and play. From personal experience, this particular chocolate bar is excellent fuel while working in an office.
I've read somewhere that it takes about 35 minutes of hard core exercise to burn off one of these 60g chocolate bars. One Mars Bar once in a while is fine. I don't eat one often, yet when I have energy to burn - I just go for it and drink plenty of water afterwards.