Wednesday, April 27, 2011

Food addiction. Chicken or egg?

Food addiction's a hot topic these days.

Proponents posit that food addiction is a real phenomenon that leads people to almost irresistibly eat.

Opponents believe that it doesn't exist, and it's just a means with which people justify their difficulties with food.

What if they're both right?

A recent study's got me thinking. Now be forewarned, it's an animal study and therefore not necessarily attributable to human beings, but nonetheless....

The study looked at minipigs (which as evidenced by the photo up above are almost unbearably cute), where brain activation of seven diet-induced obese minipigs, were compared to brain activation of nine lean minipigs following an overnight fast.

The findings were striking. The obese minipigs had a great deal more activation of their prefrontal cortices compared to the lean minipigs, where the prefrontal cortex has been shown to be involved in addictive behaviour in humans.

They also found decreased activation in the reward centres of the obese minipigs (the ventral tegmental area and the nucleus accumbens), which suggests the possibility that food "addiction" might in fact cause some sort of habituation in these brain regions which in turn would lead to individuals to require larger hits of food, to get the same brain-based reward.

But here's the thing. The minipigs, with clearly different brain chemistries, didn't self select for being obese, they were chosen to be fed more. At first they ate fairly normally, despite having ready access to food all day long (as opposed to their brethren), but then over time, and living in their all-you-can eat buffet hutches, they started to eat more. By the end of the experiment, they weighed nearly double the weight of their peers. And by the end of their experiments, their brains had changed.

This may suggest that while food addiction indeed has neurophysiologic foundations, that it's the chicken and not the egg. Meaning that these pigs weren't born addicted to food, they developed food addictions after living in what might be described as a toxic food environment.

That's exciting to me, in that if we can help people regain control over their food environments, if we can help people ease into more satiating patterns of eating, maybe we can rewire their brains, and in so doing, short-circuit these unnaturally derived neural pathways and responses.

And ultimately, I think we can. Why? Because I see it in my offices on a very regular basis (though not every time mind you, there are some folks who seem to truly struggle with these behaviours regardless of the tweaks we try).

Which is why I think both proponents and opponents are right, where food addiction has a real physiological foundation, but where there is certainly a pattern of eating that may, in some cases, predispose people to heightened neurophysiological drives to eat.

Of course when you think about it, none of this is particularly surprising. After all, couldn't the same can be said about pretty much every addiction?

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Val-Laillet D, Layec S, Guérin S, Meurice P, & Malbert CH (2011). Changes in brain activity after a diet-induced obesity. Obesity (Silver Spring, Md.), 19 (4), 749-56 PMID: 21212769