What happens to the body when you stay hungry for a long time?

Hunger for most of us is the growling of the stomach which won’t rest until you eat. When our body needs calories or energy, it signals our brain that it's time to eat, thus our stomach starts growling. This type of hunger is known as homeostatic hunger.

When the food in our stomach is completely utilised for the production of energy, our blood sugar levels and the insulin levels start dropping. When this happens, the hunger hormone, ghrelin (released in the stomach) sends a message to the hypothalamus, which then comes into action. 

Hypothalamus is a small part in the mid-brain which helps in the regulation of body functions such as sleep cycle maintenance, the release of important hormones, maintaining blood pressure and much more. Hypothalamus deploys many hormones in different parts of the body which help in the proper functioning of the body. For instance, the hypothalamus releases the hormone responsible for the body's growth, which then acts on the pituitary gland, thus releasing the necessary amount for the body. 

When the hypothalamus gets the message from ghrelin, it triggers the release of the most potent orexigenic peptide, neuropeptide Y (NPY) which stimulates the hunger. 

There is one other kind of hunger, known as the hedonic hunger, which is prevalent in some people. It is the hunger where people feel the need to eat even when their body does not demand food. Hedonic hunger is more about seeking pleasure than calories. For instance, a person who has not eaten anything in 12 or more hours would feel homeostatic hunger, whereas a person who wants a dessert after finishing a filling meal is feeling hedonic hunger.

As we start filling our stomach with food, another series of signals start processing in the body which keeps us from overeating. As the mouth, stomach and intestine give the satiety response, the fat tissues of our body release the leptin hormone.

Leptin sends a message to the brain that the body is satisfied and must stop eating. The hypothalamus then turns down the production of neuropeptide Y and starts releasing the most potent hunger-suppressing anorexigenic, peptide proopiomelanocortin (POMC) in the blood.

Before releasing POMC, hypothalamus checks the insulin and blood sugar levels to make sure that everything is back in normal limits. While this process may take a little longer, we usually feel uncomfortable after eating a large meal.

Food gives energy to the body which is necessary to stay alive. As we stop consuming food, the body starts using the stored fat and protein in the body to meet the daily glucose requirements of the brain. Your body can stay perfectly normal for 6 hours without food. After that, the body starts using the stored energy to keep the body functions working in a normal manner.

The effect of hunger slowly hits the body as initially, the body tried to cope with the lack of food but slowly and eventually, it gives up. 

First six hours of starvation 

Within the first 6 hours of starvation, the body stays normal even without food as it breaks down glycogen (the stored form of energy in the body) into glucose as and when the cells of the body require it. However, almost 25% of this energy, generated from the glycogen, is used by the brain, while the rest goes to the muscle tissues and RBCs. 

After 6 hours, the stored glycogen depletes and the body no longer has a way to produce energy, thus making you feel hungry. 

Within 6 to 72 hours of starvation

From that sixth hour to the next 72 hours, the body stays in the stage of ketosis, where the body tries to get used to fasting. As there is very little glucose left in the body, the body starts breaking down the fat present in the body to produce energy. However, fat is broken down into long-chain fatty acids which cannot be used by the brain, as the brain does not allow the entry of long-chain fatty acids. 

As there is no glucose in the body and the fats are too large to cross the blood-brain barrier, the brain starts renovating itself. So in order to get the energy, the brain starts using ketone bodies, which are the short-chain derivatives of fatty acids. But since the ketones can only meet 75% of the requirement of the brain, the brain craves glucose.

In the absence of glucose, the cognitive ability of the brain gets impaired.

After 72 hours of starvation

After 72 hours of starving, the brain starts breaking down the body’s protein as it cannot survive on just ketones. The body breaks down the protein into amino acids which are then converted into glucose, so the glucose demand of the brain is met. 

However, in the process of breaking down of the protein, the body starts destroying its own muscle mass. At this point, there is a visible loss of body fat. This breakdown of muscle mass in women can lead to the shutting down of the menstrual cycle as the body tries to reduce the energy expenditure. 

This is followed by a series of other health issues like diminished bone density, body pain and low libido. 

Without eating, the body lacks all the vitamins and nutrients, resulting in weakening of the body’s immune system in the next one to two weeks. Due to the weak immune system, the body gets prone to all kinds of diseases and even the life-threatening ones. 

After 2 weeks of starvation

Even if a person manages to survive by the second week but still continues to starve, their body keeps on using all the energy sources until all the glucagon, fat, tissue and muscle mass is completely finished. The starving person can die in 3 weeks if they do not start eating. 

The starving people after the third week usually suffer from cardiac arrhythmias or a heart attack due to tissue degradation in the heart, diaphragm and the body. They may even suffer from multiple organ failure. These conditions can be seen in a person with anorexia nervosa, an eating disorder where the person has extremely low body weight.

Hunger can affect the body of different individuals in different ways. Hunger can lead to various physical and psychological problems in both children and adults. The effects of short-term hunger are:

• Weakness
• Loss of consciousness (fainting)
• Dizziness 
• A sudden drop in blood pressure
• Trembling of hands and feet
• Headache
• Slow heart rate
• Abdominal pain

The effects of long-term hunger are: 

• Malnutrition (lack of nutrients in the body)
• Stunted growth of children due to insufficient nutrition
• Wasting in children (low weight for height)
• Reduced cognitive ability
• Visible loss of fat or muscle mass
• Thyroid dysfunction
• Low levels of potassium
• Anaemia 
• Fluctuation in the body temperature 
• Depression
• Anxiety 
• Toxic stress (stress in early childhood)
• Heart attack
• Multiple organ failure

It has been reported that starvation can lead to death in about 3 weeks or to up to 70 days. The chances of survival depend on the amount of water the person is consuming during the period of starvation and also the amount of fat in that person’s body. 

An article published in the National Library of Medicine, National Institute of Health, US, it was stated that the body can survive for 8 to 21 days without food and water. However, if a person is given access to adequate water intake, they can survive up to one to two months. 

According to a study published in the journal, Nutrition, a person needs to have a certain minimum body mass index (BMI) for survival. Body Mass Index is the way of measuring the body fat of a person based on their height and weight. As per the journal, a man needs to have a BMI of more than 13 and a woman needs to have a BMI of more than 11 to sustain life. The range of BMI that is considered normal is from 18.50 to 24.99.