We all struggle to say no to unhealthy food. It’s genetically built into us, back from our cave days when calories were scarce and sugar helped us survive. We seek to acquire calories to power our daily lives.

“Sugar is a deep, deep ancient craving,” — Daniel Lieberman, evolutionary biologist at Harvard University

Today, though, calories are anything but scarce — they’re prolific. Whether it’s Halloween, Christmas, or Sandra’s birthday at the office, unhealthy food is everywhere and impossible to turn down.

Or so I used to think.

On Halloween seventeen years ago, I spilled all my candy out from my bucket and onto the floor of our living room. I picked out three pieces for myself, and then started counting the rest.

“One, two, three… I think this one should count as two, it’s really big…six, seven…”

My mom watched me pile up all the candy in a neat stack at her side. At the end of the count, she opened her wallet and gave me $13.75. Twenty-five cents for each piece of candy, fifty cents if it was a full-size candy bar.

I took the money, relinquished the candy to my mom (who I assume donated it) and went upstairs to brush my teeth for bed.

This was my first experience with what I later learned was an actual psychological phenomenon: money is an effective way to motivate healthy choices.

Why does money work better than the promise of a longer and happier life to encourage healthy eating?

You might assume that the idea that you’ll live an extra five or ten years is enough to convince us to eat healthily. One look around your immediate environment, no matter where you are, should show you that this just isn’t true.

Eating candy is an immediate and tangible gratification. Being healthy in the future is a very far-off, abstract promise.

It’s hard for our monkey brains to grasp the fact that living longer, some day in the future, is better than snarfing down that piece of cake in honor of Sandra’s birthday right now.

Money, on the other hand, is just as immediate as a sugar rush. When I chose to give away my candy, I walked off with actual cash in hand. That was enough motivation to make what I already knew was the right choice.

How can you do this at home?

For me, I found that my motivation was greatest for buying new clothes (and buying new toys for my cats). Find something that’s going to motivate you — something stronger than just the appeal of sugar or salt. Maybe it’s a gym membership, or a charity, or even just for board games.

Every time I’m tempted to buy a candy bar, or eat one of the cookies offered at work, but I say no, I give myself fifty cents.

Every time I want to wimp out of exercising, but force myself to get out there anyway, I earn a dollar. You can set up your own financial system — it should be enough to make it worth it but not so much you’ll struggle to save it.

At the end of the month, I take the money I’ve “earned” and use it to buy myself (or my cats!) something nice.

Ultimately, we all know eating well, doing exercise, or making other healthy choices are what we really want to do. All we need is a little motivation to help us make that choice.