Feelings of hunger are, in part, governed by the circadian rhythm: physical and mental changes that correspond with a daily cycle of light and darkness.
The circadian rhythm triggers the body to release certain hormones, some of which make a person feel hungry. According to a study in the journal Obesity (Silver Spring), people typically feel most hungry in the early evening and least hungry in the morning.
However, there are various reasons why a person can wake up feeling hungry, either in the morning or during the night.
Not eating enough
If a person has not consumed enough calories, they may wake to a feeling of hunger during the night.
If a person does not consume enough food during the day, they may wake up feeling hungry.
According to the Dietary Guidelines 2015–2020, a moderately active adult female should aim to consume 1,600–2,400 calories per day, depending on how active they are. For males, the range is 2,000–3,000 calories.
If a person consumes too few calories, they may wake up hungry. Hunger is often the body's signal that it needs more energy, to make up for the amount of calories that it is burning.
Changes in exercise
If a person starts getting more exercise, they are likely burning more calories. Exercise takes up far more energy than other activities, and unless a person makes up the difference by consuming more calories during the day, they may wake up hungry.
Replacing an old exercise routine with a new one can have the same effect, even there does not seem to be an increase in physical activity.
Not sleeping enough
According to an article in the journal Sleep, disrupted sleep patterns can lead to increased appetite. This could, potentially, cause a person to wake up hungry in the night.
Night eating syndrome
If a person who wakes up hungry is eating enough during the day and generally getting enough sleep, they may have a disorder that falls into the diagnostic category Other Specified Feeding or Eating Disorder (OSFED).
According to the National Eating Disorders Association, OSFED is a serious, catch-all category that can include night eating syndrome. This usually causes a person to regularly wake up needing to eat during the night.
Authors of a study in the Psychiatric Clinics of North America point to an emerging body of research into night eating syndrome. However, at this stage, determining the best treatments will require further investigations.
How to stop it
Eating later in the evening may stop a person from waking up hungry.
It may not be immediately clear why a person is waking up hungry. They may need to use a trial and error approach to discover the cause of this experience and how to change it.
An individual may benefit from monitoring their calorie intake during the day, to make sure that they are meeting the recommended guidelines for their age and activity level.
If a person eats early in the evening, they may benefit from pushing their mealtime back a little later.
Also, it is important to get at least 7 hours of sleep per night. This is the minimum amount that a person needs to stay healthy, according to the Centers for Disease Control and Prevention (CDC).
Research into the best treatment for night eating syndrome is still ongoing. According to the Psychiatric Clinics of North America study, medication and psychological therapy are typically the approaches, though confirming their effectiveness requires more research.
Anyone who finds that they cannot stop themselves from waking up hungry should speak to a medical professional.
A person may wake up hungry for many reasons. Understanding the cause can be difficult, especially because there is a lack of research into the issue.
When trying to address it, consuming enough calories to make up for energy expenditure and getting enough sleep are good places to start.
If these strategies do not work, a medical professional is best positioned to determine the underlying cause.