A<unk>  is a strong desire to eat a particular type of<unk> . This desire can seem uncontrollable, and the person’s hunger may not be satisfied until they get that particular<unk> .<unk> s are common. One research found that ninety-seven per cent of women and 68 per cent of men reported experiencing<unk> s. There is no single explanation for<unk> s, and explanations range from low serotonin levels affecting the brain centers for appetite to production of endorphins as a result of consuming fats and carbohydrates. People often crave energy-dense<unk> s: chocolate is the most frequently craved<unk> , followed by other sweet and savoury<unk> s which are high in calories.<unk> s with high levels of sugar glucose, such as chocolate, are more frequently craved than<unk> s with lower sugar glucose, such as broccoli, because when glucose interacts with the opioid receptor system in the brain an addictive triggering effect occurs. The consumer of the glucose feels the urge to consume more glucose, much like an alcoholic, because the brain has become conditioned to release "happy hormones" every time glucose is present. Cultural differences have been found, for example, with rice being the most frequently craved<unk>  in Japan. Among low-calorie<unk> s,<unk> s for fruits are common.<unk> s tend to occur in the late afternoon and evening. The desire to eat high-calorie<unk> s increases throughout the day, while<unk>  for fruits decreases. The aspect of a<unk>  is multi-dimensional. Physiologically, it is connected with several mechanisms that motivates<unk>  seeking and prepares the body for digestion such as increased salivary flow along with activating reward-related brain areas such as the striatum. Cognitive (i.e., thinking about the<unk>  and emotional (e.g., desire to eat or changes in mood) components are also involved. A final behavioural aspect of seeking and consuming the<unk>  also occurs. Whilst experiencing a<unk>  often results in eating the craved<unk> , the<unk> -consumption relationship also depends on differences within individuals and their current situation. The<unk> s for certain types of<unk>  are linked to their ingredients. Chocolate for example, contains the neurotransmitter phenylethylamine, which is important for the regulation of the body’s release of endorphins and is responsible for the state of mood and pleasure. In recent years, researchers have focused significantly on perimenstrual<unk> s for chocolate, resulting in a better understanding of the mechanisms underlying<unk>  aetiology. Active ingredients in chocolate, known as methylxanthines (such as caffeine, theophylline, and theobromine), has been researched in relation to perimenstrual<unk>  aetiology. It has been hypothesized that women crave chocolate since methylxanthines has been shown to have the ability to alleviate physical - and perhaps psychological - symptoms associated with menstruation, such as fatigue, irritability, bloating, or cramps. It seems intuitive to assume that the emergence of a<unk>  might indicate that the body is low in a specific nutrient, vitamin or mineral. Understanding the reason behind a<unk>  could lead to confidently supplying the body with that missing<unk> . However, evidence for this is inconsistent and relatively poor. For example, when participants had to consume a nutritionally balanced, liquid diet, they reported more<unk> s than during a baseline period, and<unk>  could be induced by imagining their favourite<unk>  although participants were satisfied. Further, females tend to respond with more negative affect to indulging their<unk> s than men. During pregnancy - a time during which the body needs more energy and certain nutrients than usual - it seems that the types of craved<unk> s do not differ from usually craved<unk> s, and even if women crave unusual, potentially harmful,<unk> s or other substances, it seems that this is rather driven by social factors than by physiological needs. Similar interpretations have been derived from perimenstrual (chocolate)<unk> s which, for example, do not disappear after menopause, making hormonal mechanisms unlikely. There are basic associations between nutrient deficiency and<unk> s, but they appear to account for a small fraction of<unk> s at most. Instead, several psychological explanations for why and how<unk> s emerge have been developed. Prominent models are based on (Pavlovian) conditioning.
Food craving
Fear of flying
Sundowning
Fear of trains
Fear of needles
Thirst
Fidgeting
Sniffing 