Symptoms of Not Eating

Symptoms of not eating can vary based on your age, general health, and how long it has been since you last ate. Over the short term, not eating enough can lead to hypoglycemia (low blood sugar) and symptoms like fatigue, shakiness, and nausea. If a person continues not to eat, they may experience slurred speech, confusion, syncope (fainting), and even seizures.

Not eating enough over the long term can lead to malnutrition, manifesting symptoms like thinning hair, skin changes, muscle loss, frequent illness, infertility, and, in extreme cases, cachexia (wasting).

This article describes the symptoms of not eating enough and complications that can develop if this persists. It also describes the symptoms that warrant an immediate visit to a healthcare provider.

Early Symptoms

When you are in a fasted state (meaning that you have stopped eating), the body's normal metabolism changes. Metabolism is the process of converting the calories from foods you eat into energy.

One of the most immediate effects of not eating is hypoglycemia in which your body's main source of energy—glucose (blood sugar)—drops steeply. The lack of fuel can trigger an array of side effects, including:

• Headache
• Extreme hunger
• Difficulty concentrating
• Tiredness
• Sluggishness
• Nausea
• Dizziness
• Shakiness
• Weakness
• Pale, clammy skin
• Rapid heartbeats
• Irritability or anxiety
• Imbalance and loss of coordination
  

Eating food, particularly simple carbohydrates, can reverse hypoglycemia and these symptoms relatively quickly.

Symptoms of Prolonged Fasting

When fasting is prolonged, the body will turn to other energy sources for fuel in the absence of glucose. It does so by breaking body fat down into fatty acids, which are then converted by the liver into ketone bodies . Ketone bodies serve as a backup energy source when glucose is not available.

The process of conversion is known as ketosis , which can trigger symptoms like:

• Sudden weight loss
• Dry mouth
• Bad breath
• Extreme fatigue
• Weakness
• Insomnia and nighttime waking
• Muscle spasms and cramps
• Decreased appetite
• Constipation or diarrhea

If you are entirely without food, the process of ketosis typically occurs within 72 hours. If you are eating too little food, it may take longer.

At the same time, the emptying of the body's glucose reserves can lead to symptoms of severe hypoglycemia, including:

• Blurred vision
• Slurred speech
• Confusion
• Sleepiness
• Fainting
• Nightmares
• Seizures

Complications of Not Eating

One of the longer-term complications of not eating enough is malnutrition. Malnutrition occurs when you either do not eat not have enough to eat, are not eating enough of the right things, or are not absorbing nutrients from foods you eat.

When the body continues to become deficient in calories, it cannot receive all of the carbohydrates, proteins, fats, vitamins, and minerals it needs to keep the body functioning normally.

You may be malnourished if you unintentionally lose 5% to 10% of your body weight within 3 to 6 months or your body mass index (BMI) is under 18.5. BMI, however, is a dated, flawed measure; it doesn't take into account factors such as body composition, ethnicity, sex, race, and age.

Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

When this weight loss happens, symptoms of malnutrition can develop, including:

• Hair loss
• An unhealthy, pale appearance
• Loss of muscle tone
• Weakness
• Fatigue
• Frequent infections
• Irregular or no periods
• Easy bruising
• Inability to stay warm
• Diarrhea
• Loss of appetite
• Irritability
• Apathy

Rare Symptoms

The prolonged absence of nutrition causes the body to decline. A person may start experiencing long-term symptoms of malnutrition such as:

• Brittle hair and nails
• Glossitis (inflammation of the tongue)
• Stomatitis (inflammation of the mouth)
• Fine, downy body hair ( lanugo )
• Dry or yellowish skin
• Infertility
• Slow wound healing
• Prolonged bleeding from wounds
• Osteopenia (bone thinning) and fractures
• Arrhythmia (irregular heartbeats) and palpitations
• Cachexia (a wasting syndrome causing dramatic weight loss)

How Much Is Too Little Food?

The Dietary Guidelines for Americans recommends that adult females get at least 1,600 calories a day and adult males get at least 2,200 calories a day. These are the minimum values for weight maintenance. Anything less may deprive you of the nutrients you need to function normally.

Other Complications by Group

Different groups of people are affected differently by not eating enough food. This is because people of different ages have different nutritional needs, and those with certain chronic diseases may have special dietary needs.

Infants and Young Children

Infants and children have key differences in their metabolism that cause them to use up more protein, glucose, and lipids to maintain their baseline energy. This can cause them to show symptoms of not eating more quickly than adults.

Infants and children who are not getting enough to eat may be lethargic (not responsive), sleeping more than normal, and be fussy or irritable.

Teenagers

Teens may have delayed growth or appear short in stature. They may also lack the usual symptoms of puberty due to disruptions in hormones from lack of glucose and calories.

Decreased caloric intake in older children and teens may also cause fragile bones, learning difficulties, and mood problems (like depression or irritability).

People With Chronic Conditions

People with certain chronic conditions may have a greater demand for nutrition. These include conditions like:

• Diabetes: Not eating can be especially dangerous for people with diabetes because they take medications to lower their blood sugar. They need to check their blood sugar regularly and practice healthy eating habits to prevent blood sugar crashes.
  
• Cancer: People with cancer, especially those receiving chemotherapy, may experience a loss of appetite, digestion issues, and mouth sores. All of this can lead to not wanting to eat. Studies suggest that anywhere from 20% to 70% of people with cancer are malnourished.
• Sickle cell disease: Children and adults with sickle cell disease (SCD) have a higher metabolic demand and require more calorie and protein intake than others. Poor nutrition in people with SCD can lead to joint pain, infection, anemia, and an increased risk of hospitalization.
• Gastrointestinal diseases: Chronic illnesses such as Crohn’s disease, ulcerative colitis, or celiac disease can reduce the absorption of nutrients your body needs (malabsorption). This can contribute to malnutrition even if you are eating enough.

When to See a Healthcare Provider

If you are experiencing any of the following after a period of not eating, seek immediate emergency care:

• Vomiting or diarrhea that won’t stop
• Persistent rapid heartbeat
• Chest pain
• Bleeding that won’t stop
• Difficulty staying awake
• Trouble breathing
• Slurred speech
• Disorientation or confusion
• Seizures
• Inability to speak, see, walk, or move

Summary

Symptoms of not eating can develop due to hypoglycemia and ketosis, causing mild symptoms like fatigue and dizziness to more serious ones like heart palpitations and seizures. A common complication of not eating is malnutrition, which can lead to missed periods, infertility, bone mineral loss, and severe wasting.

Children who are malnourished are at risk of brittle bones, learning difficulties, and depression. People with chronic diseases may need additional nutrition to meet the body's demand for calories, protein, minerals, and other nutrients.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

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By Brandi Jones, MSN-ED RN-BC
Jones is a registered nurse and freelance health writer with more than two decades of healthcare experience.

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