Dr. Andy

Reflections on medicine and biology among other things

Sunday, September 11, 2005

An experiment of one

One thing I find frustrating about health and fitness as opposed to medicine is the lack of data. If you want to know if, say, angiotensisn converting enzyme (ACE) inhibitors improve mortality after myocardial infarction (MI) there are multiple randomized trials with thousands of participants, meta-reviews of the trials, etc. But if you want to know how to taper before an ultramarathon, the best data available is anecdotes from other runners and occasional expert opinion; if you're lucky you might find a small unblinded study of 20 total athletes.

This weeks Freakonomics column in the NYT magazine deals with Seth Roberts, a psychology professor who has made a habit of conducting experiments on himself.
Most intriguing to me is the diet that has apparently allowed him to lose 40 lbs while eating whatever he wants:
After a great deal of experimenting, he discovered two agents capable of tricking the set-point system. A few tablespoons of unflavored oil (he used canola or extra light olive oil), swallowed a few times a day between mealtimes, gave his body some calories but didn't trip the signal to stock up on more. Several ounces of sugar water (he used granulated fructose, which has a lower glycemic index than table sugar) produced the same effect.

The theory behind this is convoluted, to put it mildly. He first notes that the body has a "set point" of weight it tries to maintain. The idea here is that there are mechanisms that act over long periods of time (weeks to years) that keep your weight more or less steady. This is clear in animals studies and seems to be the undoing of most human diets (losing weight is relatively easy, keeping it off hard).

He second believes that the set point is affected by the relative abundance or scarcity of foods. Evolutionarily, we are probably designed to eat a lot when food is abundant (successful hunt or harvest time) but also go through periods of relative deprivation (winter, tough years). Roberts thinks (and there may be some evidence for this) that you are actually less hungry during times of scarcity.

It is not entirely clear to me why taking in unflavored calories between meals helps, but I guess the idea is that you tend to eat bland food during times of scarcity.

I've wondered if my current diet (fasting 1 day per week) also helps move my "set point" downwards by tricking my body to take in think food is scarce. I've also noted that you are far less hungry than you would think during a fast. When I run in the morning of fast days, my hunger peaks at breakfast and declines during the day. I do have a sort of awareness that I'd like to eat that is distinct from what I'd generally call hunger


At 6:30 PM, Anonymous Jason said...

This may be totally anecdotal too, but I had heard (and now I can't remember where), that someone had discovered that high fructose corn syrup somehow did not trigger the body's calorie counter. Therefore, the opposite of what you are after occurred; people who ate a lot of high fructose corn syrup tended to keep gaining weight. The set point kept moving higher.

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