Are we "meant" to drink milk? No other mammal, after all, drinks milk after infancy, and certainly not another species' milk. Are we "meant" to eat cake? Bonobos and chimpanzees don't eat cake, and they're our nearest living relatives. But we are not bonobos nor, for that matter, any other mammal.

We've all gotten "the look" or a lecture as we buttered a dinner roll or consumed its equivalent sin. "What? What am I doing wrong? The fat in the butter? The dairy? The white flour in the roll? The yeast?" Receiving other people's unsolicited dietary advice only tightens my grip on my fork and whatever's on it.

We hear it over and over: portion control, portion control, portion control if you want to lose weight. And it's true: As a general rule, the more foo...