Michael Pollan famously started his 2008 book, In Defense of Food: An Eater's Manifesto, like this: "Eat food. Not too much. Mostly plants."
This simplicity appeals in a marketplace of processed, fortified, promoted food "products" that modern Westerners navigate every day.
It's easy to identify manufactured foods that lead to quick and steady weight gain, right? Soft drinks, certainly. Any food with a lot of sugar is easily stored by the body as excess fat. But what about some of these foods long held as healthy, or at least a healthier option:
* Wheat is something your body can live without, says Dr. William Davis in his 2011 book, Wheat Belly. Ancient wheat may have been OK, but today's wheat has been so hybridized during the last 50 years that human bodies have not had a chance to adapt to it, and that's before you get to questions of genetically modified crops.
Lose the wheat -- even allegedly "heart healthy whole grain" products, he says -- and notice which of these conditions improve: obesity, diabetes, high blood pressure, excessive snacking, rheumatoid arthritis, irritable bowel syndrome.
* Artificial sweeteners really help people cut calories without having to give up favorite treats, and have long been used by diabetics in coffee or candy to avoid fast and steep rises in blood sugar. But there is evidence that they don't work the way everyone always assumed.
Susan Swithers, a behavioral neuroscience professor at Perdue University, spoke about research on the subject on a recent episode of NPR's "Science Friday." The human brain learns with experience how to react to different foods. When a person tastes something sweet, the body prepares to deal with it by releasing the right hormones that help regulate how much to eat and to keep blood sugar in a healthy range, she said. Artificial sweeteners deliver the sweet trigger, but not the expected calories. Over time, this body's system for regulating blood sugar and appetite become confused and less effective. The risk becomes apparent in people who consume as little as three diet soft drinks a week, she said.
* Even 100 percent fruit juice is not a healthy substitute, writes Dr. Robert H. Lustig in his recent book Fat Chance: Beating the Odds Against Sugar, Processed Foods, Obesity and Disease. Fruit juice certainly has some nutritional value, so in that way it is better than the empty calories of soda. But a piece of fruit is full of fiber, which among other things, slows the body's ability to digest the high sugar content and helps to keep blood sugar in a healthy range. In juice, the fiber has been removed, so there is nothing to blunt the blood sugar jolt, Lustig says.
Trying to keep up with nutrition and dietary advice can be an exhausting, frustrating, full-time endeavor. The modern food world is complex, so people's knowledge must be complex, too. But every breakthrough comes back to the same result: Favor whole foods, processed as little as possible, over altered, manufactured ones.