The Science of Willpower

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Why Dieting Turns You Into a Zombie

When you cut calories, your brain cells eat themselves.

We all know that starving yourself to lose a few pounds can zap your energy and kill your mood.

But would you believe that dieting turns you into a literal zombie? That's right: cut back on the calories, and you become a brain-eating zombie whose appetite cannot be satisfied. And the brain you're eating? Yours.

The science behind this disturbing notion is a new study in the August issue of Cell Metabolism. Researchers at the Albert Einstein College of Medicine have discovered that food restriction induces brain cells in the hypothalamus to shift into self-annihilation mode. The brain cells start to eat themselves (a cell process called autophagy) in an act of martydom. You see, the neurons in the hypothalamus that become zombies normally regulate your appetite. When these cells gobble themselves up, it produces a hunger signal. Thanks to their self-sacrifice, you're suddenly motivated to end the famine and feed the brain.

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Why does calorie restriction prompt this bizarre brain response? It may be a survival mechanism that kicks in when available energy stores start to run low. When you diet, the body's typical energy stores are depleted more quickly than your body -- and brain -- are used to. The brain is particularly sensitive to changes in energy supply. The zombie cells may be eating themselves to fuel the brain's high energy demands; the hunger response may be an adaptive side effect.

Either way, it helps explain why you feel like the walking dead when you take dieting to the extreme -- and become obsessed with your next meal. As the zombies say, "Mmmmm, brains."

Study:

Kaushik S, Rodriguez-Navarro JA, Arias E, et al (2011). Autophagy in Hypothalamic AgRP Neurons Regulates Food Intake and Energy Balance. Cell Metabolism, 14, 173-183.

 

Kelly McGonigal, Ph.D., is a health psychologist at Stanford University.

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