Ok, I posted about this because it sounded so convincing, but then read criticisms of it (such as this one) … I’m leaving my original post up below here because, well, it’s what I posted, but I’m really curious to see what else comes up about this — some of the criticism seems to focus on one or another bit of Roberts’ ‘theory’ but not the whole thing.

Anyway… Here’s my original post.

I just read a paper written by a psychologist at Berkeley. He builds on the accepted concepts that the brain has a certain ‘setting’ where it wants to keep each individual person’s body fat, and that it can be affected. He proposes that it’s the relationship between the stimulus of taste (which has to be very similar from one meal to the next) closely followed by caloric intake registering in the brain, which causes the brain to pump out the chemistry that keeps fat on our bodies.

A food is fattening (raises the set point) to the extent its flavor is associated with calories.
The strongest flavor-calorie associations will occur, learning research implies, when four things are true: (a) the flavor is strong and complex flavor; (b) the food is digested quickly; (c) the food is eaten repeatedly; and (d) the flavor is exactly the same from one instance to the next. These four traits combine in a multiplicative way in the sense that if one is entirely absent, the food will not raise the set point at all.

It’s confusing reading in places, but it’s amazing — it starts making more sense about 5-6 pages into it, when the examples are more concrete and there’s less quoting of previous academic stuff.

Here’s the article: http://freakonomics.com/pdf/whatmakesfoodfattening.pdf

The article that pointed me to it was on the Freakonomics website:
http://freakonomics.com/times0911.php

It explains why the South Beach thing works (and explains why the South Beach explanation for why it works isn’t the whole story, though I don’t think they ever really say South Beach? — they just talk about low-GI diets in general)

Basically, your brain will choose one kind of food over another if it gives a quicker/higher caloric boost and it also tastes better. In the US, there’s such an abundance of this kind of food, especially fast food and most grocery store branded products, that our brains naturally gravitate toward this stuff. The sameness of the food from one eating to the next is very important too: even some slight differences in taste can throw this mechanism off. But because so many foods (even in groceries and non-fast-food restaurants now, like Chilis and whatnot) are available nation-wide or in every neighborhood and always taste the same, our brains can avail themselves of this experience in ways unprecedented in human history until recently.

In low-glycemic-index (low GI) foods, they may taste great even, but because they take longer to digest and the calories take longer to hit the bloodstream and register in the brain, the effect isn’t the same (it’s the overlap between taste and calorie-registering that over time bumps up the brain’s need to eat certain foods to keep fat stores high, because we’re evolved to keep them high in times of plenty). I’m way over-simplifying this, but anyway, it makes so much sense!

The paper goes on to explain why it used to be that the poor in the US were thin while the rich were fat, and why it’s reversed. (Although in most countries the poor are still pretty thin.)