Question #1: Energy

I recently read an advertisement for a skin care product that claimed 'Suddenly, skin is full of energy . . .' It got me thinking; is there any means of getting energy into our body other than consuming calories? And when I say energy, I mean the capacity to perform work. Steve, I think I remember you saying this on one of your 'Great Courses' lectures but I wanted to confirm. Specifically I'd like to know if caffeine gives us energy or simply increases our metabolism. I also remember 'energy' was the word Rebecca selected at last years (2013) NECSS as being misunderstood by the general public. Please lift the veil just a little more. I hope this is not a topic you've discussed before and I've simply forgotten. If it is, please accept my apologies and move on to your next message. Thanks. David Young Hong Kong PS: If your interested, the product name is the serum and it's produced by Cle de Peau Beaute Laboratories. They have a website but the product may be marketed differently in different countries. Here in Hong Kong the advertisements claim the product can add energy to your skin.