Science Explains Why You Want To Eat Even When You're Not Hungry

When in 1862, writer and poet Emily Dickinson wrote (via KQED): "The heart wants it wants or else it does not care," she might as well have been writing about our relationship with food. Hunger may be easy to satisfy — experts talk about reaching for fruit or something else healthy for snack, or to bypass simple snacking for a balance of protein, fats, and carbs for a full meal instead. But to meet, never mind satisfy, a craving? That's another matter altogether.

Many of us may think that our cravings are a sign that our bodies are in need of specific vitamins and nutrients — for instance, Healthline points out that some people believe chocolate cravings are a sign of low magnesium levels, and yearning for meat or cheese can be interpreted to mean your iron and calcium levels are low. But science says our bodies don't work in such a straightforward way, and cravings are proof of that.

Scientists at the University of Liverpool say that feeling hungry isn't just a case of: meeting a biological need, as in our stomachs growl when we need nourishment, and then that same organ hits the kill switch when we've had enough to eat. Instead, physical hunger is actually controlled by physiological signals which tease our appetites until we eat, and then cut off that appetite when we get full. 

But there's another system inside us that tells us its ok to have rich or high-energy food, and that's our brain reward system. Unfortunately, that reward system is able to override our sense of fullness or our satiety signals — and it also makes us more susceptible to temptation. The trouble is, eating high-calorie foods (just think about a gorgeous piece of chocolate cake, a chocolate chip cookie, or perhaps a bazillion-calorie cinnamon bun) isn't always the best choice, nutrition-wise. "This anticipated enjoyment is a powerful motivator of our food intake," the University of Liverpool researchers Charlotte Hardman and Carl Roberts write in The Conversation. "The sight and smell of food attracts our attention, and we may start to think about how nice it would be to eat. This may result in cravings and food consumption."

This food reward system, which is supported by our complex brain structures, may be more active in some people than in others, so their desire to give in to cravings is much stronger. Imaging scans show that the brains of people who crave chocolate regularly are more active when they see or taste chocolate than people who don't look for this velvety treat. This same reward system also helps us build a link between certain conditions and eating food, so we end up with associations like summer means ice cream; seaside means fish and chips; and movies mean popcorn.

These findings are especially helpful for people who, for one reason or another, need to get their cravings under control. As BBC Future points out, our world is full of triggers that can encourage these cravings in advertising and in social media. "Everywhere we go, we see adverts for food with lots of added sugar, and it's easy to access these foods," Mount Sinai School of Medicine assistant professor Nicole Avena says. "This continual bombardment of advertising affects the brain — and smelling these foods primes the brain to want to eat them."

But since there is no way to avoid the stimuli, scientists are now trying to get people to overcome their cravings by using the power of the mind instead. Some studies suggest mindfulness techniques can work to cut cravings, and the University of Liverpool researchers also suggest developing coping strategies that keep us from eating food when we don't need it.