hunger, appetite and obesity. is it all in the head?

Did you know that your brain is approximately 60% fat? So if you have ever been called “Fathead”, it’s actually not too far from the truth. However if your total body fat is 60% then we have ourselves a problem. I have read a lot recently about how the brain controls the body and some of these studies got me thinking.

Phantom Limb Pain (PLP) for instance has been studied for over 50 years and we are still struggling to pinpoint the mechanisms behind it. PLP is basically pain, a real pain, which exists in a limb that is no longer there for whatever reason, typically amputation. So we know that the pain can’t be originating in the limb. It must be the nervous system (brain, spinal chord and nerves). Similarly, there are studies whereby an individual puts their hand in a box, and then sees a video of their hand apparently being pin pricked when it is not actually their hand. The individuals report the pain simply because they think they are being pin pricked! Pretty cool huh?! If the body has this relationship with pain, then could it be the same with other things such as hunger and appetite?

 To tell you about this next study, I need to give you a bit of background about the science, but I’ll try to keep it short and not bore you. Appetite and body fat storage are driven by a selection of hormones such as testosterone, cortisol, insulin, leptin, ghrelin and others. Ghrelin for instance is produced in the gut when no food has been there for a while. It sends a signal to the brain telling it about a lack of food and this in turn makes you hungry. So, more ghrelin equals more hunger and a bigger appetite. As you would expect, when you do eat food, ghrelin is suppressed and hunger goes away.

So this particular study, measured ghrelin levels in two groups of participants after giving them each a type of food. Group 1 were given a boring low fat, low sugar milkshake of only 104 calories. They were shown a picture with the stats and told about how boring it was. The other group were given a super duper high sugar, high fat milkshake obviously bursting with taste, flavour and a whopping 600+ calories. Again they were shown the stats and told about how disgustingly bad for their waistline it would be. Ghrelin levels were measured in both groups before and after consuming the milkshake. The group having the boring slimline milkshake only showed a very small  drop in ghrelin levels whereas the second group with the super bad for you milkshake showed a much larger substantial drop in ghrelin levels, reducing any hunger pangs.

Or so the participants thought. In actual fact both groups were given the same 300 calorie milkshake. Amazing huh? The ghrelin levels, either reducing appetite, or not, were completely driven by the nutrition information that they participants were given. So could it be that the brain is also controlling hunger and appetite instead of any physiological processes within the body?
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If you have been on a diet recently, you probably noticed that you were hungry. This raises the question, were you hungry because you had cut down the quantity of food consumption or was it because you know you were on a diet and the brain was controlling your hunger? So next time you feel hungry, ask yourself if you really are.