I picked up this metaphor from an off-hand comment by a Buddhist monk in the book The Jew in the Lotus. But I've expanded on it considerably. Religion can be looked upon as food. Consider the laws and rules that make us better people. Treat others as you would want to be treated. Practice loving kindness. Respect the environment. Reach out to that mystical something inside of you that can make you whole. This is religion's nutrition--Its fiber, protein, and vitamins. But there's more to religion than that. There's myth and ritual--celebrating holidays, listening to and repeating the stories, singing songs, and so forth. This is the seasoning, the herbs, the flavors that makes religion joyful and attracts people to it. This is the difference between Chinese food and Italian food, and the difference between one religion and another. But consider fast food. It's all about flavor, with only the slightest pretense of nutrition. And it's addictive. That's fundamentalism.