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Picture warm, gooey cookies,

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crunchy candies,

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velvety cakes,

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waffle cones piled high with ice cream.

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Is your mouth watering?

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Are you craving dessert?

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Why?

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What happens in the brain

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that makes sugary foods so hard to resist?

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Sugar is a general term

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used to describe a class of molecules

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called carbohydrates,

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and it's found in a wide variety of food and drink.

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Just check the labels on sweet products you buy.

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Glucose,

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fructose,

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sucrose,

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maltose,

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lactose,

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dextrose,

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and starch

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are all forms of sugar.

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So are high-fructose corn syrup,

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fruit juice,

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raw sugar,

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and honey.

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And sugar isn't just in candies and desserts,

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it's also added to tomato sauce,

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yogurt,

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dried fruit,

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flavored waters,

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or granola bars.

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Since sugar is everywhere,

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it's important to understand

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how it affects the brain.

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What happens when sugar hits your tongue?

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And does eating a little bit of sugar

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make you crave more?

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You take a bite of cereal.

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The sugars it contains

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activate the sweet taste receptors,

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part of the taste buds on the tongue.

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These receptors send a signal up to the brain stem,

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and from there, it forks off

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into many areas of the forebrain,

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one of which is the cerebral cortex.

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Different sections of the cerebral cortex

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process different tastes:

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bitter,

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salty,

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umami,

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and, in our case, sweet.

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From here, the signal activates

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the brain's reward system.

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This reward system is a series

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of electrical and chemical pathways

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across several different regions of the brain.

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It's a complicated network,

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but it helps answer a single, subconscious question:

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should I do that again?

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That warm, fuzzy feeling you get

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when you taste Grandma's chocolate cake?

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That's your reward system saying,

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"Mmm, yes!"

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And it's not just activated by food.

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Socializing,

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sexual behavior,

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and drugs

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are just a few examples

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of things and experiences

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that also activate the reward system.

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But overactivating this reward system

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kickstarts a series of unfortunate events:

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loss of control,

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craving,

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and increased tolerance to sugar.

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Let's get back to our bite of cereal.

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It travels down into your stomach

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and eventually into your gut.

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And guess what?

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There are sugar receptors here, too.

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They are not taste buds,

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but they do send signals

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telling your brain that you're full

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or that your body should produce more insulin

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to deal with the extra sugar you're eating.

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The major currency

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of our reward system is dopamine,

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an important chemical or neurotransmitter.

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There are many dopamine receptors in the forebrain,

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but they're not evenly distributed.

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Certain areas contain dense clusters of receptors,

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and these dopamine hot spots

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are a part of our reward system.

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Drugs like alcohol,

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nicotine,

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or heroin

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send dopamine into overdrive,

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leading some people to constantly seek that high,

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in other words, to be addicted.

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Sugar also causes dopamine to be released,

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though not as violently as drugs.

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And sugar is rare among dopamine-inducing foods.

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Broccoli, for example, has no effect,

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which probably explains

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why it's so hard to get kids to eat their veggies.

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Speaking of healthy foods,

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let's say you're hungry

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and decide to eat a balanced meal.

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You do, and dopamine levels spike

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in the reward system hot spots.

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But if you eat that same dish many days in a row,

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dopamine levels will spike less and less,

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eventually leveling out.

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That's because when it comes to food,

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the brain evolved to pay special attention

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to new or different tastes.

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Why?

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Two reasons:

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first, to detect food that's gone bad.

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and second, because the more variety

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we have in our diet,

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the more likely we are

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to get all the nutrients we need.

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To keep that variety up,

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we need to be able to recognize a new food,

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and more importantly,

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we need to want to keep eating new foods.

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And that's why the dopamine levels off

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when a food becomes boring.

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Now, back to that meal.

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What happens if in place

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of the healthy, balanced dish,

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you eat sugar-rich food instead?

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If you rarely eat sugar

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or don't eat much at a time,

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the effect is similar to that of the balanced meal.

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But if you eat too much,

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the dopamine response does not level out.

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In other words, eating lots of sugar

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will continue to feel rewarding.

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In this way, sugar behaves a little bit like a drug.

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It's one reason people seem to be hooked

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on sugary foods.

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So, think back to all those different kinds of sugar.

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Each one is unique,

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but every time any sugar is consumed,

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it kick-starts a domino effect in the brain

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that sparks a rewarding feeling.

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Too much, too often,

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and things can go into overdrive.

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So, yes, overconsumption of sugar

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can have addictive effects on the brain,

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but a wedge of cake once in a while won't hurt you.