Think back to your most productive workday in the past week. Now ask yourself: On that afternoon, what did you have for lunch?

When we think about the factors that contribute to workplace performance, we rarely give much consideration to food. For those of us battling to stay on top of emails, meetings, and deadlines, food is simply fuel.

But as it turns out, this analogy is misleading. The foods we eat affect us more than we realize. With fuel, you can reliably expect the same performance from your car no matter what brand of unleaded you put in your tank. Food is different. Imagine a world where filling up at Mobil meant avoiding all traffic and using BP meant driving no faster than 20 miles an hour. Would you then be so cavalier about where you purchased your gas?

Food has a direct impact on our cognitive performance, which is why a poor decision at lunch can derail an entire afternoon.

Here’s a brief rundown of why this happens. Just about everything we eat is converted by our body into glucose, which provides the energy our brains need to stay alert. When we’re running low on glucose, we have a tough time staying focused and our attention drifts. This explains why it’s hard to concentrate on an empty stomach.

So far, so obvious. Now here’s the part we rarely consider: Not all foods are processed by our bodies at the same rate. Some foods, like pasta, bread, cereal and soda, release their glucose quickly, leading to a burst of energy followed by a slump. Others, like high fat meals (think cheeseburgers and BLTs) provide more sustained energy, but require our digestive system to work harder, reducing oxygen levels in the brain and making us groggy.

Most of us know much of this intuitively, yet we don’t always make smart decisions about our diet. In part, it’s because we’re at our lowest point in both energy and self-control when deciding what to eat. French fries and mozzarella sticks are a lot more appetizing when you’re mentally drained.

Unhealthy lunch options also tend to be cheaper and faster than healthy alternatives, making them all the more alluring in the middle of a busy workday. They feel efficient. Which is where our lunchtime decisions lead us astray. We save 10 minutes now and pay for it with weaker performance the rest of the day.

So what are we to do? One thing we most certainly shouldn’t do is assume that better information will motivate us to change. Most of us are well aware that scarfing down a processed mixture of chicken bones and leftover carcasses is not a good life decision. But that doesn’t make chicken nuggets any less delicious.

No, it’s not awareness we need—it’s an action plan that makes healthy eating easier to accomplish. Here are some research-based strategies worth trying.

The first is to make your eating decisions before you get hungry. If you’re going out to lunch, choose where you’re eating in the morning, not at 12:30 PM. If you’re ordering in, decide what you’re having after a mid-morning snack. Studies show we’re a lot better at resisting salt, calories, and fat in the future than we are in the present.

Another tip: Instead of letting your glucose bottom out around lunch time, you’ll perform better by grazing throughout the day. Spikes and drops in blood sugar are both bad for productivity and bad for the brain. Smaller, more frequent meals maintain your glucose at a more consistent level than relying on a midday feast.

Finally, make healthy snacking easier to achieve than unhealthy snacking. Place a container of almonds and a selection of protein bars by your computer, near your line of vision. Use an automated subscription service, like Amazon, to restock supplies. Bring a bag of fruit to the office on Mondays so that you have them available throughout the week.

Is carrying produce to the office ambitious? For many of us, the honest answer is yes. Yet there’s reason to believe the weekly effort is justified.

Research indicates that eating fruits and vegetables throughout the day isn’t simply good for the body—it’s also beneficial for the mind. A fascinating paper in this July’s British Journal of Health Psychology highlights the extent to which food affects our day-to-day experience.

Within the study, participants reported their food consumption, mood, and behaviors over a period of 13 days. Afterwards, researchers examined the way people’s food choices influenced their daily experiences. Here was their conclusion: The more fruits and vegetables people consumed (up to 7 portions), the happier, more engaged, and more creative they tended to be.

Why? The authors offer several theories. Among them is an insight we routinely overlook when deciding what to eat for lunch: Fruits and vegetables contain vital nutrients that foster the production of dopamine, a neurotransmitter that plays a key role in the experience of curiosity, motivation, and engagement. They also provide antioxidants that minimize bodily inflammation, improve memory, and enhance mood.

Which underscores an important point: If you’re serious about achieving top workplace performance, making intelligent decisions about food is essential.

The good news is that contrary to what many of us assume, the trick to eating right is not learning to resist temptation. It’s making healthy eating the easiest possible option.

More on food, health, and productivity:

Should You Eat While You Negotiate?

Sleep Is More Important than Food

Sitting Is the Smoking of Our Generation