Hacking the Weight-O-Stat (with Sprinkles!)
“Shangri-La? Odd name for a diet. Name of a spa, maybe.”
--Seth Roberts, The Shangri-La Diet
A few months ago I
wrote about the interactions
between classical conditioning and the immune system, treating the
immune response as an insanely complicated reflex. I implied, based
on a small amount of research, that drug responses could be imagined
the same way, and encouraged SF writers to explore the idea in story
form. This month, I want to push that envelope even further, to
include weight control, as proposed in an unpublished review
paper and a best-selling diet
SF has spent a long
time predicting that humans of the future might evolve away from
their prehistoric muscular physicality, either by diverting ever more
of their metabolic resources to their brains
or, as in Wall-E, by bloating up into immobile
couch potatoes who rely on technology to run their
lives. I've never seen anyone write about how that might actually
happen, mechanistically. Our current pop-culture model of weight
control is some sloppy intuitive combination of a thermostat and a
thermostat model: when weight goes down, we get hungry, and we eat.
What happens when weight goes up? A good thermostat would turn off
the heat, and maybe turn on the AC. It is obvious from common
experience that obese people still get hungry, but we haven't updated
our mental model to reflect this. Medicine, victim to the same naïve
model, has searched and searched for faulty metabolic wiring in the
weight-o-stat, and there are a few rare syndromes, like leptin
deficiency, that have excited hopes of an easy pill
cure, but none of these can account for the current obesity epidemic.
genetic studies may change this; it seems that the “thrifty
gene” that was hypothesized to underlie obesity may be older
than we thought. Still, genes will only be part of the answer.
primate social circuitry kicks in to assign blame, like it does with
any other addiction. Maybe the weight-o-stat is overridden by
culture, by advertising, or by a vague weakness of character. We may
even assume that obese people are lying about their hunger, or
(invoking depth psychology) that they are lying to
themselves—hallucinating their hunger, in a sense.
I don't deny that there
is a psychological/behavioral dimension to obesity, that we eat to
comfort ourselves, or that we eat because of social demands (though
people about these relationships does not appear to work very well).
Any behavior as biologically important as eating gets tangled up with
individual learning and all kinds of cultural dynamics (which require
measures to untangle). It's precisely the
multidimensional nature of the problem that I find so interesting.
Roberts, who I mentioned in a previous column on
stepped back to re-imagine the problem of overeating. What if, for
the sake of argument, we drop our cheater-detection game theory
assumptions and imagine that obese people are telling the truth about
their experience of real hunger? What if the weight-o-stat is not
broken? What if the weight-o-stat is working perfectly for the hungry
environment in which it evolved?
We know that many
mammals, such as rodents and bears and even one primate (the mouse
lemur), gain lots of weight, specifically
storing energy as fat, and then lose
it again during hibernation or torpor. Roberts
proposed that as mammals, humans might have a similar bias towards
weight-gain, but controlled by different signals. We evolved near the
equator, so the day-length
cues that most hibernating mammals use to prepare for
winter would not have worked (though those signals are so old,
they might still be accidentally relevant now that we have
spread around the world). The fact that humans lived in famine-prone
tropical environments, variable in their rainfall and such, means our
ancestors needed a system that would prime them to gorge whenever
food was available, on the assumption that soon it would not be. They
rarely had a chance to stay fat enough, for long enough, to develop
the health problems we see so often today.
proposed that humans, as nomadic omnivores with extremely varied
diets, needed a weight-gain signaling system that was flexible enough
to accommodate many different foods, some of which the species had
never encountered before. Every time we invaded a new continent, we
found new ecosystems, full of unique foods. This is where the link to
the other previous column on conditioning becomes important. We have
to like new flavors (anyone who honestly remembers his or her first
beer will know what I mean). The more often we experience a
particular flavor-calorie association, the stronger it gets, and the
more fattening a particular food becomes. This leads to a number of
which is extremely consistent by design (that being their
definition of quality control), should be more fattening than more
variable home-cooked food, even when made with the same calorie
and calories in time should weaken the association, reducing hunger
and allowing weight loss. This was the basis for The Shangri-La
Diet, which basically recommends that we eat unflavored calories
between meals to reduce hunger. This scheme requires that sweet and
fat be considered calorie signals, not flavors in the
technical sense that the model uses the word.
the flavor-calorie associations should also weaken them enough to
turn off the weight-gain signal. This was my personal favorite
because it led to a wacky series of experiments where subjects lost
weight by putting spearmint sprinkles on their mashed potatoes one
meal, and sprinkles of another flavor, like chocolate, the next
meal. Really neat SF-type thoughts there.
There might be lots of
other clever ways to hack the system, ways that require only
creativity and persistence. We might not have to engineer artificial
hormones, or undigestible
pleasure foods, or alien temporal fistulas that teleport food out of
your stomach before your small intestine can absorb it (though I
guess those would be cool, too).
Now, what the
weight-gain signal actually was, Roberts never got specific about. He
seemed satisfied with the circumstantial evidence cited in his review
paper. My own hypothesis is that it’s due to a conditioned
insulin release. We know that insulin can drop blood
sugar and trigger hunger. I have personally experienced something
like this during those periods in my life when I've had regular daily
NOON = HUNGRY!
But twenty minutes
later, not so much. My longest personal fast, during an academic
summer on a college campus where my parents weren't watching, lasted
about three days, and hunger came and went in somewhat predictable
mealtime cycles. That makes no sense in a weight-o-stat model
whose only input is a measure of bodily energy reserves. Hunger
should grow continuously until cut off by an input of calories, or
saturate at a steady maximum level. However, short-term spikes of
intense hunger make perfect sense in a classical conditioning model,
where the unconditioned response is calorie-driven hunger, the
conditioned stimulus is time of day, and the conditioned response is
a pulse of insulin, producing a time-driven hunger. This conditioned
hunger could presumably happen even in an obese person.
We've now seen three
examples of conditionable behaviors, two unconscious (immune
suppression and drug response) and one more or less conscious
(eating). The novel/movie A Clockwork Orange famously used
aversive conditioning, similar to what is used in real
life with sheep-killing predators, to affect sex and
violence in its human protagonist. What other non-creepy
possibilities are there?
Ph.D., drives home to Kentucky every year for Thanksgiving. His mom
makes the best damn cornbread on this planet or any other.
Why was this paper never published? That is a very good question, and one I wish I had the answer to.
To summarize, Slate disagrees.
Questionnaires are always fraught measures, and should always be seen as only a first step towards finding real answers.
Ecological Momentary Assessments are sort of like research tweets. Subjects are
pinged at random times to report whatever the researchers are interested in. It’s about the most unbiased method anyone has
come up with. If you’ve never read a systematic review, this shows the rules for deciding which studies count and which don’t,
in convenient flow-chart form.
OK, maybe more than one.
“Survival of the fattest?” Another reason for a credits system in science—knowing who to blame for the bad puns. Seriously,
though, folks, check this one out. Mutant apes in Europe during the Miocene, frogs storing fat in their feet,
and many other wonderful examples. Imagine if your feet weighed 20 pounds apiece.
Check out Figure 7 for a schematic diagram of the process.
These rodents can be triggered to gain weight just by leaving the lights on. A lot of humans leave the lights on, too. Hmmm . . .
Siberian hamsters are also a model system for studying the effects of day length on body weight. More detailed wiring diagrams of the hypothalamus in this one.
I read this book on vacation, and it is fantastic.
This study is about people who already like beer. I predict they would get different results from a first-beer situation.
Two words: “anal leakage.”
Paired with odors of rosewood and peppermint, in this case, but a clock might work, too.
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