They can come out of nowhere - often when you're sitting at your desk during a busy afternoon.
And until you satisfy them, they're all you can think about.
Food cravings are rarely for carrot sticks or broccoli.
They are for something sweet or salty or full of caffeine and we usually fix them by scoffing a packet of chips or reaching for the lolly jar.
While the cause of some cravings is psychological, some desires can indicate your body needs a specific nutrient or is lacking what it needs to perform at its best.
Accredited practising dietitian Dr Deborah Nolan-Clark from Landmark Nutrition says there is a difference between simply enjoying a food and craving one.
"The key things to think about are the desire must be intense, that we'd go out of our way to get it, and it's relating to a specific food, there's a specific food need that must be met."
The most common cravings are for sweet and carbohydrate-rich foods and salty morsels.
An intense desire for sugar can be triggered by stress, by feeling tired and dietary restrictions.
But it can also indicate a low level of serotonin in your blood stream, a compound that acts as a neurotransmitter to send signals to your brain about your mood.
"When you eat sugar it actually increases your absorption of an amino acid called tryptophan and that actually helps the body to make serotonin," Nolan-Clark says.
"It can help with increasing your mood, decreasing your anxiety and improve overall well-being, so a lot of the reason people crave sugar is because of a decrease of their levels in serotonin."
Women are particularly susceptible to this craving when they are pre-menstrual. Studies have found they have a lower concentration of serotonin during this time.
A genuine physiological craving for salt can indicate dehydration and often occurs after a prolonged period of exercise or illness.
If this is the case, you need to give your body sodium, usually by drinking a sports drink.
But Nolan-Clark says most salt cravings are simply due to a love of the taste.
Spicy food cravings are less common, but recent research has shown eating spicy dishes can trigger the release of endorphins, which are chemicals that can boost your mood. Giving in to your cravings is fine if they're occasional, but constantly resorting to highly processed foods can be a problem if it leads to weight gain and means you are missing out on other nutrients.
If this is the case, you need to seek healthier alternatives.