I’m hungry. No, really, I’m not kidding. I’m not just calmly and pleasantly considering the possibility of a future meal. I’m famished. Ravenous. And I have to eat now.

But here’s the thing: Obviously, I’m not literally starving. One look at me in a bathing suit makes it pretty clear that I’ve got energy stores. There is no emergency. I know where my next meal is coming from. My refrigerator is full of food. I know I don’t have to eat right now.

And yet, I have to eat right now. And not just anything. It has to be salty, or crunchy, or contain at least 95% chocolate. Nothing else will do.

Most people have experienced food cravings, and some people experience them daily. So what gives? Are your cravings some secret biochemical code for something your body really needs? Or is it something else? Where is the disconnect between hunger and cravings?

Actually, scientists have studied this question a lot, and they’ve come up with some interesting answers. As it turns out, cravings are complex and they might mean one thing on one day and another thing on another day. Once you narrow down what’s likely causing yours, you can address them with knowledge rather than by whim. Because really, who’s in charge? You or the cupcake? (Don’t answer that yet.)

Let’s consider why you might be having cravings, and what you can do about them.

Not enough nutrients

I had the weirdest experience the other day. My 13-year-old son keeps reminding me that we own a beautiful new juicer, and a few mornings ago, he urged me to make fresh juice for breakfast. We juiced a pineapple, green apples, kale, Romaine lettuce, a piece of fresh ginger, and a big cucumber, and we shared the tasty results. It was delicious, super nutrient-dense, and after I had a big glass of it, I wondered what else I wanted for breakfast. And then I realized I didn’t want anything else. In fact, I was totally satisfied until lunchtime.

I have the same experience when I make a smoothie, with a big handful of leafy greens, a cup of fresh or frozen berries, unsweetened almond milk, and sometimes a scoop of high quality protein powder. When my diet hasn’t been particularly nutritious, a sugar-free smoothie or juice made with plenty of fresh vegetables and fruit really calms my cravings. It’s nutritional therapy.

When you aren’t getting enough nutrients, your body knows it, and broadcasts the message that you need something. But your brain might not always interpret the nutritional deficiency accurately. “I need calcium” may come out as, “I need large amounts of cheese melted on top of tortilla chips.” Flood your body with nutrient-dense foods on a daily basis, and your body will be more likely to hum along happily without complaining.

This morning, my son suggested we have a daily fresh juice happy hour after school. Out of the mouths of babes…

It’s a habit

Perhaps surprisingly, cravings are often simply a matter of habit. Whenever I go to the movies, I crave a certain treat in a yellow box (it involves dried fruit and chocolate; need I say more?) not because I need it, but because I’m used to having it. It’s the same with ice cream after dinner while watching “American Idol,” or always getting that certain banana chocolate chip muffin at that certain coffee shop. It begins to feel necessary, but of course it’s not.

Fortunately, habits can be broken. If you’ve ever quit drinking coffee or biting your nails, you know that it’s grueling for a few days, but then it gets easier. The trick is to replace the bad habit with a better habit.

Lately, when I go to the movies, I bring my own supply of mixed nuts and dried fruit. It satisfies the same craving and it’s much better for me. Instead of ice cream, try nonfat Greek yogurt mixed with fresh berries and sliced almonds–and maybe even a tablespoon of mini chocolate chips, when it’s the “American Idol” finale. Bake a better muffin at home, enjoy, then go have your coffee with your friends. You came to see them, not the muffin, right?

Planning ahead to subvert one habit with another works. Whether your habit is nighttime noshing, a mid-afternoon candy bar, or that morning muffin, once your healthier replacement becomes a new habit, chances are your old habit will seem unappealing, as in, “I can’t believe I used to eat that!”

The power of suggestion

I like to think I’ve got a powerful brain. I got good grades, I pick up new skills quickly. So why is it that when I see someone eating a cookie, I become a brainless zombie with a vacant stare, staggering towards the pantry mumbling, “Must…eat…cookie…?”

We’re visual creatures, we humans, and we like pleasure. So sue us. But just because you see it doesn’t mean you have to have it. Even though it feels that way.

If this sounds like you, it’s time to recognize that you are letting your whims control your actions, when your logical brain should be the one calling the shots. This is like allowing your toddler to take over your bookkeeping. It can come to no good.

So the next time you see something that sparks a craving, whether on a cleverly designed television commercial or behind the glass case at a bakery or in the hands of someone else, give your inner toddler a time out and consciously decide whether you really want to eat that.

Waiting too long to eat

Some people can go all day without eating, and then have a salad. I suspect these people are actually aliens. For most of us, eating is necessary for sustained energy, concentration, and the ability to function.  If you wait too long to eat, you’re going to get too hungry, and then your inner beast takes over and you end up devouring whatever’s in your range of vision.

Don’t put yourself in that position. Don’t go longer than four hours without eating something nutritious, unless you are sleeping. Don’t skip meals. Snack. Keep the nutrients coming in, and if necessary, stock your bag, your car, and your desk with the good stuff, like apples, almonds, carrots, bananas, oranges, yogurt, peanut butter, wholegrain crackers, hummus, and celery sticks. Then if you still want chocolate, you’ll have a much easier time having just a square or two.

Blood sugar crash

A really strong craving for carbohydrates (like baked goods, sweets, or bread) is often the result of a blood sugar crash. Here’s how it can happen: You eat a doughnut, a cookie, or some candy. This floods your bloodstream with glucose. Your body responds by releasing insulin, to shuttle the glucose into the cells. But if you’ve got too much glucose because you ate more sugar than your body can handle, your body needs to release a lot of insulin. This effectively banishes glucose, dropping your blood sugar too low, and triggering more intense cravings. You’ve thrown your system out of balance. Too much blood sugar, followed by too much insulin, followed by a craving for another infusion of too much sugar.

This is why a breakfast of doughnuts or toaster pastries or waffles drowned in syrup can make you hungry all day. This is why you intend to eat three cookies and a few hours later, you polish off the package. If you are susceptible to this cycle, watch out. Too much of this blood sugar monkey business can result in metabolic syndrome, which is a pre-diabetic condition, and you don’t want to go down that road.

The solution: Cut out the junk carbs. Every time you eat, make sure your carbohydrates are mostly vegetables, fruits, and whole grains, and always include some protein with every meal and snack. Never, ever eat simple carbohydrates alone. Get off the roller coaster.

Here’s my final word of advice: Every time you make a choice, you have the chance to make a good one, no matter what choices you’ve made before.

So who’s in charge? That’s right. You are. Don’t let a cupcake or a bag of fries be the boss of you. No matter what happened yesterday or this morning or ten minute ago, keep taking back the wheel. Nobody’s perfect, but it’s what you do most of the time that matters.

And now, if you’ll excuse me, it’s happy hour, and I believe the juice bar is open.