Why Do We Crave? The Science Behind Food Cravings

(Editor’s note: This article is from a past issue of Brain World magazine. If you enjoy this article, please consider a print or digital subscription!)

My new diet requires me to eat sprouts and steamed veggies for dinner. On most days, it’s fine. Not all the time. Every day, as I fill my boyfriend’s more colorful and much richer plate — Indian curries with rice, or chicken tikka rolled in egg wraps — I find myself craving his dinner. Often, I just let go and grab a bite or two from his plate.

Let’s face it: Cravings can sometimes overpower you and compel you to consume sumptuous
food that is not always healthy. But they are a reality of life.

Hunger or Craving?

According to the Merriam-Webster Dictionary, a craving is a “very strong desire for something.” You could crave a donut, a glass of wine, or a cigarette. Even sex. All of us have felt like slaves to our food cravings at some point — it’s just a matter of how long until we give in. The million-dollar question: How do food cravings work? Our evolutionary history provides some clues.

“Our brains evolved to respond to food whenever the opportunity was available, especially if the food was palatable and delicious,” says Kent Berridge, a professor of psychology and neuroscience at the University of Michigan. “Now, cues for delicious food are around us all the time, much more than the evolutionary history. Our brains naturally respond to those cues to eat.”

Most people would equate cravings with hunger. It turns out that’s not quite the case. “Hunger is an input to the brain’s craving system; it can amplify the craving system. But the brain’s craving system works a little separate from the hunger system,” says Berridge. “The brain’s reward system is really the brain’s craving system.”

The hunger loop operates out of the hypothalamus at the base of the brain. The reward system, on the other hand, is located in the center of the brain. It involves many regions of the brain, such as the ventral tegmental area, the nucleus accumbens, and the prefrontal cortex. In a 2012 NeuroImage study, women volunteers were shown images of household objects and different types of food, with varying levels of delectability. The researchers looked at their brains using an MRI. The number of potato chips the women consumed after the scan directly corresponded with the activity in their nucleus accumbens — the captain of the reward and motivation ship.

The reward circuitry exists to make you feel good when you participate in activities that are important for survival, such as eating, drinking, and sex. So, when you eat a delicious cheeseburger, especially when you’re hungry, the reward system releases a neurotransmitter called dopamine that triggers feelings of pleasure. The reward pathway is connected to areas associated with memory and behavior. So once you finish your meal and find it pleasurable (reward), your brain will remember this behavior and make sure you repeat it in the future.

The reward mechanisms that control cravings are very similar to the ones in addiction. “We think that cravings for drugs and food (particularly so-called ‘hedonic foods’ that are high-fat, high-sugar) are very similar,” says Natalia Lawrence, senior lecturer in translational medicine at the University of Exeter. “Brain imaging studies suggest that pictures of drugs (and alcohol/tobacco) and hedonic foods activate similar brain regions (involved in learning, memory, and motivation).”

What Triggers Cravings?

Hunger and craving manifest themselves in different ways. “Hunger is our body’s natural reaction to needing nourishment,” says Cynthia Dsauza, assistant professor of Addictive Disorders and Recovery Studies at Texas Tech University. “Onset of hunger can result in stomach rumbling, mild headache, or feelings of weakness. Hunger doesn’t go away with a passage of time.” On the other hand, Dsauza explains, cravings can be triggered by outside influences, such as a tiff with your boss, relationship troubles, and even social gatherings.

Cravings are often specific for certain types of foods. All of us have had that evening when all we wanted was that extra-cheese pizza from the eatery around the corner. “Cravings typically do go away with a passage of time and can arise even after we have eaten,” says Dsauza. Why do people generally crave carb-heavy, unhealthy food? “Because cravings are typically psychological and not physiological (unlike hunger), they tend to be satisfied by a feeling or sensation that is gained from eating certain foods,” says Allison Childress, nutritionist at Texas Tech University. “Through brain imaging studies we know that certain foods (sugar) can elicit a euphoric feeling.”

Moreover, personal cues — pictures, smells, memories of foods — can trigger cravings. A person’s emotional cocktail can also drive the urge to eat. “Both negative emotions (stress but also sad mood, depression, boredom) and strangely enough positive emotions (being excited, relaxed when socializing) can increase cravings,” says Lawrence. “Some people may be more inclined to eat/take drugs to relieve negative emotions, others to ‘get high’ and ‘party’.”

Research shows that stress can also have an impact on people’s eating habits. A University of California, San Francisco, rat study published in the Proceedings of the National Academy of Sciences found that chronic stress could play a role in overeating. “Fast food tends to be cheap, fast, and loaded with fat, salt, or sugar. When we eat these kinds of foods during times of stress, we teach our brains that those kinds of foods make us feel better,” says Dsauza. “Over time this becomes a habit and if you don’t learn how to deal with your stress in positive ways (like exercise, hobbies, quiet time) you might get caught up in a pattern of disordered eating.”

Lifestyle choices can also govern cravings. A University of California, Berkeley, study showed that poor sleeping habits can make people crave unhealthy foods. Using functional MRI scanning, they found out that people ate unhealthy food when they were deprived of sleep, and, conversely, consumed healthy food after sleeping to their heart’s content. The scientists noted impaired activity in the front lobe, the part of the brain involved in complex decision making, after sleep deprivation, while brain areas that govern rewards were buzzing with activity.

As with most things, different people react to cravings in a different manner. “Some people have loss of control when faced with appetizing foods, are not able to feel full or satisfied, and they may think about food more than other people do,” says Childress. “These people react strongly to the sight or smell of foods, and the amygdala region of their brain becomes activated and then remains activated until the food is gone.” Childress adds that women tend to have weaker control over their food cravings compared to men.

Keeping Cravings In Check

Cravings can easily wreck any healthy-eating resolutions, and eventually any long-term weight-loss goals, but it is possible to keep them in check. “Instead of fighting them, accept food cravings as a normal part of everyday living. We are surrounded by food,” says Childress. “We can’t always control our environment, but we can control how we react to that environment.” Childress recommends eating three well-balanced meals per day, getting sufficient exercise and rest to keep cravings at bay. Or, maybe wait till the time a drug made from the Gila monster lizard’s saliva makes it to the market! Research at Gothenburg University, Sweden, showed that such a drug could control cravings in rats.

(Editor’s note: This article is from a past issue of Brain World magazine. If you enjoy this article, please consider a print or digital subscription!)

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