“You’re only being a good scientist,” Katz said, “if you say, ‘I’m going to try to read the literature in as unbiased a manner as I possibly can, see where it leads me, and then offer the advice that I have based on that view from an altitude.’ I don’t see that going on here, and again, I think it’s kind of sad because I think the public is being misled.”

“I also find it sad that because his book is filled with a whole bunch of nonsense, that’s why it’s a bestseller; that’s why we’re talking. Because that’s how you get on the bestseller list. You promise the moon and stars, you say everything you heard before was wrong, and you blame everything on one thing. You get a scapegoat; it’s classic. Atkins made a fortune with that formula. We’ve got Rob Lustig saying it’s all fructose; we’ve got T. Colin Campbell [author of  The China Study, a formerly bestselling book] saying it’s all animal food; we now have Perlmutter saying it’s all grain. There’s either a scapegoat or a silver bullet in almost every bestselling diet book.”

It feels like all of them -- the no carbs, the no sugars, the no glutens -- are all pointing at the same phenomenon. 

It's the chemistry of addiction to foods that make the brain want more of them. 

I don't know if I buy that elevated sugar levels affect the brain in negative ways.  For one thing it's hard to get anything to cross the blood brain barrier, second thing wouldn't the body regulate what goes to the brain, or through the circulatory system to the brain?  Also what if the sugar was elevated for a period of time, what would it be doing at the cellular level that would be, I'm guessing, killing cells?  Is sugar toxic to cells?  or is it the engine of cellular activity?

"Glucose is the form of sugar that travels in your bloodstream to fuel the mitochondrial furnaces responsible for your brain power. Glucose is the only fuel normally used by brain cells. Because neurons cannot store glucose, they depend on the bloodstream to deliver a constant supply of this precious fuel."

http://www.fi.edu/learn/brain/carbs.html

"Too much sugar or refined carbohydrates at one time, however, can actually deprive your brain of glucose – depleting its energy supply and compromising your brain's power to concentrate, remember, and learn. Mental activity requires a lot of energy."

I've read article after article that natural sugar from fruit affects the brain in a very different way than processed sugar (high fructose syrups) and artificial sweeteners.

It's the processed and refined sugars that have such a bad effect.

That makes sense, eat sugar in it's real form: fruit.  Definitely stay away from the highly processed sweeteners like HFCS.

Right! For bonus points do the same with grains. 

Whole grains are ok; bleached and enriched are not. 

The simplest rule is to minimize the amount of highly processed food you eat. If it is packaged eat as little of it as you can. That will make the base of your food pyramid fresh vegetables. They should form the majority of your diet. 

The second rule, and one harder to attain, is to learn what your food allergies and intolerances are (if any). Knowing these lets you know what healthy foods to eliminate, and what to replace them with. Are you lactose intolerant? No dairy. Nut allergy? No nut butters, etc. 

Scientifically engineered to be addictive foods like Doritos should be completely avoided. In fact, anything with a list of ingredients containing words you don't understand (or for the food chemists out there more that 4 syllables) should be eaten rarely or eliminated. 

The hardest part of a healthy diet is the lack of convenience. The food spoils more quickly. You have to learn to cook beyond dumping the contents of a torn open package on a plate and heating it in the microwave. For the poor it can be next to impossible, because the cheapest food with the longest shelf life is the sugar and preservative laden garbage. 

But that very first rule, if you can manage it, will get rid of most of the unhealthy sugar in your diet.