February 26, 2013 | 4
I have decided that one of the ways I will utilize this new blog space is to comic-ify other SciAm posts. This week, I felt inspired by Scicurious‘s post about food “addictions:” Of course I’m stressed, I’m in cookie withdrawal.
To study the withdrawal-like effects of stopping a high fat diet, researchers took two groups of mice — one that had been on a low fat diet for 6 weeks, and one that had been on a high fat diet for 6 weeks. Both groups were then put on a normal diet and tested to see behavioral effects. How do you test mouse diet-related behavior? You give them a lever that, when pressed, gives them a juicy morsel of junk food.
In self-administration, you give a mouse a lever. When he hits the lever, he gets a sucrose pellet, or a high fat pellet, depending on the day. What you are looking at here specifically is something called a progressive ratio. This is supposed to measure how motivated an animal is to get something rewarding, by measuring how HARD the animal is willing to work. So at first he presses the lever once, gets a pellet. Win. He presses the lever again, but this time he has to press 2 times. Then 4. Then 8. Then 16. And so on. The “breakpoint”, is the point at which the animal just gives up and decides it’s not worth the work. This is a paradigm used a lot in studies of drug reward, and it works for tasty food as well.
So what happened? Well, the mice that had been on a low fat diet reached their breakpoint rather quickly.
The mice that were coming off their high fat diet were far more determined to get more junk food, and willing to go to town on that lever.
The same study also looked at how diet changes affect anxiety levels. And sure enough, the mice going through high fat diet withdrawal were more anxious than the mice that were on the low fat diet, measured by how much time they would spend in open spaces in a maze. Poor little guys. Read more about this at Scicurious.
While Scicurious is cautious about calling food itself addictive (seeing as how without it we would die), the pleasure reward response we get from junk food can be. And just like any addictive substance, you eventually need more and more of it to get your “fix” as your brain adjusts. So do be careful around cookies.
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