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Wednesday, May 7, 2008

Why Hunger Makes You Eat Crap

The best recipe for poor food choices and weight gain is to only eat when you are hungry.

This is best done by skipping meals and allowing yourself to get so hungry that you will end up eating anything edible, no matter how bad for you.

Obviously, if you are hungry and have the choice, last night's leftover pizza will prevail over carrot sticks.

So why is it more difficult to make healthy food choices when you are hungry?

Because healthy foods are seldom your favorite foods and usually not the ones that trigger your reward centres and make you feel happy and content.

Hey wait a minute! Did you not in a previous blog entry remember me making the distinction between hunger (homeostatic) eating and appetitive (hedonic) eating?

Well, it turns out the two systems are more closely linked than we may have thought - at least according to a new paper by Saima Malik and colleagues from McGill University, Montreal, Canada, just out in CELL METABOLISM.

Malik and colleagues infused the "hunger-hormone" ghrelin into volunteers and used functional MRI to look at what parts of the brain were activated in response to pictures of junk foods or scenery (controls).

It turns out that not only did ghrelin (as expected) increase the sensation of hunger, but it also increased brain activity in the amygdala, orbitofrontal cortex, anterior insula, and striatum which form part of the mesolimbic reward system involved in addictive behaviours.

This finding is new, because so far ghrelin was largely associated with the homeostatic system - i.e. the system that is more concerned with ensuring energy balance rather than the hedonic system - i.e. the system that is more about the reward you get from eating foods you like.

When you think about it, this finding sure makes sense. After all if you are hungry (and have a choice) you may as well eat the foods that you enjoy.

Unfortunately in today's world that may also mean that you are more likely to chose energy-dense foods that make you feel good, which in turn makes you eat too much - a sure recipe for weight gain.

So while in clinical practice it may make sense to distinguish between homeostatic and hedonic hyperphagia, it is important to remember that biologically the systems are linked and ingestive behaviour may well display characteristics of both systems at a given meal.

It is indeed a fine line between biological need and addiction.

Edmonton, Alberta

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