Why Your Brain Can’t Resist Reese’s

Ahead of Halloween, I’m thinking about self-control and king-sized candy bars.

Dana G Smith
Elemental
Published in
4 min readOct 27, 2020

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Image: Perry Gerenday/Getty Images

This is a modified excerpt from Inside Your Head 🧠, a weekly newsletter exploring why your brain makes you think, feel, and act the way you do, written by me, Elemental’s senior writer and a former brain scientist. Subscribe here so you won’t miss the next one.

Your brain wants Halloween candy 🍫

I have a pretty gnarly sweet tooth. Like, “can’t keep a pint of ice cream in the freezer because I’ll finish it” kind of sweet tooth. My fiancé, on the other hand, can’t really be bothered about sugary treats. He’ll literally take a bite out of an Oreo and put the other half of the cookie back in the bag. (He may also be a serial killer for that move, but that’s another article.)

Our different, ahem, strategies were put to the test last week when he bought a two-pound bag of Halloween candy in case we had any trick-or-treaters this Saturday, and the bag disappeared four days later. The mystery of the missing candy remains unsolved…

But it got me thinking: Why do some people have self-control around desserts while others are seemingly insatiable?

Part of the answer is genetic. Based on research of identical and fraternal twins — who share 100% and 50% of their genes, respectively — scientists have learned that genes account for about 30% of people’s reactions to sweet tastes.

Some people have variations in genes that affect their taste buds, making sugar taste sweeter to them. Unsurprisingly, those people also typically report eating more sugary foods.

Another study found that a gene that controls the levels of a hormone produced by the liver influences people’s preference for sweets. Your liver releases the hormone after you eat sugar or carbohydrates, which are converted to glucose in the body. The hormone signals to the brain that it doesn’t need any more glucose, resulting in you feeling satisfied. However, some people have a genetic variant where the default level of this hormone is lower than normal, leaving you constantly craving cookies.

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Dana G Smith
Elemental

Health and science writer • PhD in 🧠 • Words in Scientific American, STAT, The Atlantic, The Guardian • Award-winning Covid-19 coverage for Elemental