We all get cravings for specific foods every now and then, and those cravings can be so strong, they almost feel involuntary, like your body is missing some nutrient it can get from a muffin. This isn't typically how cravings work, though.
As SciShow explains, cravings are a lot more psychological than they are physiological. Host Michael Aranda says that they're usually tied to different emotional triggers, like stress. He explains:
Eating a butter frosted cupcake or a bag of salty fries releases an opioid typhoon that lights up the brain's pleasure center and makes us feel awesome ... cravings are also tied to your brain's memory centre, which explains why you might also crave a food that isn't full of fat or sugar. Your brain could be tying that food to a happy memory or a reward, and thinking about the memory associated with that food can make you crave that food.
Marci Pelchat of the Monell Chemical Senses Center told Smithsonian magazine that there are indeed some extreme deficiencies that cause cravings, but generally, cravings aren't our body's way of telling us we need something. For more detail, check out the full video.
What Causes Food Cravings? [YouTube]