It is possible to pass out from not eating. This temporary loss of consciousness, medically termed syncope, occurs when the brain does not receive an adequate supply of blood, which carries the necessary glucose for its function. Understanding this can help in recognizing and preventing such episodes.
How Not Eating Affects Your Body
The body relies on glucose, a simple sugar, as its primary fuel source, especially for the brain. When you do not eat, your blood glucose levels can drop, a condition known as hypoglycemia. A blood glucose reading below 70 milligrams per deciliter (mg/dL) often signifies low blood sugar.
Initially, the body uses glucose in the bloodstream. Without food, it taps into stored glucose, called glycogen, primarily found in the liver and muscles. Once these glycogen reserves are depleted, which can happen after about 8 hours without food, the body starts breaking down fats into ketone bodies for energy. This shift, combined with low glucose, reduces brain fuel, leading to impaired function and loss of consciousness.
Recognizing the Signs and Who is at Risk
Before fainting from lack of food, the body often sends warning signals. These can include dizziness, lightheadedness, shakiness, sweating, and feeling weak or tired. Other signs include a rapid heartbeat, blurred vision, difficulty concentrating, irritability, or confusion. Further drops in blood sugar can lead to slurred speech, trouble walking, or even seizures.
Some individuals are at higher risk. Risk factors include prolonged fasting, skipping meals, or an unbalanced diet. People with diabetes, especially those on insulin or other blood-sugar-lowering medications, are particularly vulnerable if medication isn’t balanced with food. Intense physical activity without adequate carbohydrate consumption can also deplete glucose stores. Excessive alcohol consumption also impairs the liver’s ability to release stored glucose.
Preventing and Managing Fainting Episodes
To prevent fainting from lack of food, regular and balanced meals are advisable. Eating regular, balanced meals every three to five hours, including snacks, helps maintain stable blood sugar. Staying hydrated is also beneficial, as dehydration can contribute to feeling faint.
If you feel faint, immediate action can help prevent a fainting episode. Lying down with your legs elevated or sitting with your head lowered between your knees can help increase blood flow to the brain. Consuming a quick source of sugar, such as 15 grams of carbohydrates from fruit juice, regular soda, glucose tablets, or hard candies, can rapidly raise blood sugar. Recheck blood sugar after 15 minutes and repeat if it remains low. Seek medical attention if fainting episodes are frequent, prolonged (lasting more than a minute), or accompanied by chest pain, shortness of breath, or an irregular heartbeat.