Dear Mark: Your Brain on Junk Food

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by Mark Sisson: 10
Ways to “Get Primal”



Clearly, we
eat not just to fill our stomachs but to satisfy a whole host of
biochemical drives. The brain is built to incentivize our efforts
not just with the quieting of hunger
but the kick-starting of an intricate hormonal “reward”
system. When it comes to diet, I’ve always said what nurtures
the body nurtures the brain. The proof is in the biochemical picture.
And while I wholeheartedly believe that we each choose what we eat
and how we treat our bodies, there’s something to the science
that shows addictive properties in junk food. I occasionally get
emails on this topic. Here’s a timely one from last week.

Dear Mark,

wondering if you believe in junk food addiction. I’m very new
to the Primal Blueprint diet and have been having some serious issues.
I feel like it’s one step forward two steps back some days.
For instance, I fell off the wagon entirely at Halloween, thinking
a few pieces from my kids’ stash wouldn’t be a big deal
for a couple days. But a few pieces turned into a whole backslide.
I found myself roaming the house for days afterward craving foods
I thought I was done with. I’m finally getting back on track
now, but I’ll admit I’m a little stunned. I don’t
want to make excuses for myself (no one made me eat the stuff to
begin with), but is there something more complicated here than I

I know there
are those in this community who consider themselves recovering sugar
addicts, so to speak. Some regularly offer their comments on the
boards/forum threads, and others have written me personally about
the difficulty of breaking
this first “wall” on the way to going Primal.
When you’re addicted to sugar (or carbs in general), even a
day’s break can make you feel like a rabid fiend scouring for
your next fix. Cutting
all grains
in addition to sugar (since grains readily convert
to glucose) will be critical for your success in this case. In fact,
you probably can’t eliminate a long-term sweet-toothed sugar
without eliminating grains.

An interesting
study presented at the Society for Neuroscience conference last
month gets closer to the biochemical reason for this. As researchers
observed rats that were fed a steady diet of “junk food,”
(chocolate, cheesecake, bacon, sausage, etc.) they found that the
“’animals’ brain reward circuits became less responsive’”
over time. Not surprisingly, the animals began to exhibit “compulsive
overeating habits.” Even when subjected to mild shocks, the
animals were undeterred as they chowed down on the junk food, and
they refused to eat healthier food when it was the only feed available.
In essence, the junk food dulled their pleasure centers. As a result,
they kept seeking out the junk food and eating in an attempt to
trip the reward trigger, but the blunted neurological response was
never enough. This diminishing of pleasure center response, the
researchers added
(PDF), paralleled what they have witnessed in rats “’as
they become addicted to cocaine or heroin.’” (Comforting,

Other studies
have shown similar findings. Using human brain imaging, researchers
have found lower dopamine (linked to reward and pleasure response)
receptor levels in obese people compared to subjects in their recommended
weight range.

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