When we lump unlike things together, it confuses us and opens holes in our theories. I'm not normally one to read about diets, dieting advice, or anything of that sort, but in today's article about the Shangri-La Diet, I saw an important distinction that no one's talked about. Something Eliezer said in the comments struck me as odd:

a skipped meal you wouldn't notice would have me dizzy when I stand up

And a few posts later,

I can starve or think, not both at the same time.

Reading these, I thought, that's not what being hungry like feels like for me. But while being hungry doesn't feel like that, those descriptions were nonetheless familiar. And then it hit me.

He wasn't describing the symptoms of hunger. He was describing the symptoms of hypoglycemia, more commonly known as low blood sugar. Blood sugar is one of the main systems responsible for regulating appetite, so for most people, having low blood sugar and being hungry are one and the same. The main focus of the Atkins diet, for example, is reducing swings in blood sugar, thereby reducing appetite. The Shangri-La diet seems like it would have a similar effect.

Followup to:  Beware of Other-Optimizing

Once upon a time, Seth Roberts (a professor of psychology at Berkeley, on the editorial board of Nutrition) noticed that he'd started losing weight while on vacation in Europe.  For no apparent reason, he'd stopped wanting to eat.

Some time later, The Shangri-La Diet swept... the econoblogosphere, anyway.  People including some respectable economists tried it, found that it actually seemed to work, and told their friends.

The Shangri-La Diet is unfortunately named - I would have called it "the set-point diet".  And even worse, the actual procedure sounds like the wackiest fad diet imaginable:

Just drink two tablespoons of extra-light olive oil early in the morning... don't eat anything else for at least an hour afterward... and in a few days it will no longer take willpower to eat less; you'll feel so full all the time, you'll have to remind yourself to eat.

Why?  I'm tempted to say "No one knows" just to see what kind of comments would show up, but that would be cheating.  Roberts does have a theory motivating the diet, an elegant combination of pieces individually backed by previous experiments:

• Your metabolism has a set point, like the setting on a thermostat: when your weight is below the set point, you feel hungry; when your weight is above the set point, you feel full.
• But the set point is not a constant; it is raised and lowered by what you eat.
• This mechanism in turn seems to be regulated by a flavor-calorie association.  (Possibly as a famine-storage mechanism that tries to store more resources when dense food sources are available.)  If you eat something with flavor X, which is followed by your metabolism detecting a large source of calories, flavor X will (a) seem more appealing and taste better, and (b) will raise your set point whenever you eat items with flavor X.
• Your set point is always naturally dropping, but is raised by eating; usually these forces are in dynamic balance and your weight stays constant.

I'm not going to go into all the existing evidence that backs up each step of this theory, but the theory is very beautiful and elegant.  The actual Shangri-La Diet is painfully simple by comparison: consume nearly tasteless extra-light olive oil, being careful not to associate it with any flavors before or after, to raise your body weight a little without raising your set point.  Your body weight goes above your set point, and you stop feeling hungry.  Then you eat less... and your weight drops... and your set point drops a little less than that... but then next morning it's time for your next dose of extra-light olive oil, which once again puts your (decreased) weight a bit above the set point.  The regular dose of almost flavorless calories tilts the dynamic balance downward.  That's the theory.

Many people, including some trustworthy econblogger types, have reported losing 1-2 pounds/week by implementing the actual actions of the Shangri-La Diet, up to 30 pounds or even more in some cases.  Without expending willpower.

I tried it.  It didn't work for me.