Through the ages, fasting has been a religious ritual. More recently it has become a way to make political statement. The notion that abstaining from food for periods of time can improve your health and cure disease is a much more recent idea.
Fasting is a part of religious observations for Catholics during Lent, and Mormons fast on the first Sunday of each month. Many Protestant religions encourage fasting on special days of prayer and some American Indian tribes fasted to bring luck and avoid disaster. Muslims fast during the month of Ramadan, Jews fast on Yom Kippur and Hindus fast during some of their festivals.
Fasting is also done for political reasons. Mahatma Gandhi went on hunger strikes as a method of active nonviolent resistance to improve conditions in India in the early 1900s. Now, prisoners and the politically disenfranchised all over the world embark on hunger strikes to draw attention to their causes.
In the United States, conventionally trained doctors, nurses and dietitians rarely recommend fasting to their patients, but naturopaths and other alternative-medicine advocates sometimes do.
Preliminary research has shown that medically supervised fasting may help some people with diseases such as diabetes and rheumatoid arthritis.
The notion that fasting rids bodies of toxins is debatable. Your liver and kidneys are constantly detoxifying your blood, meaning they neutralize and filter out harmful substances from what you consume: food, alcohol, medications and herbs.
Some believe that fasting speeds up this process by releasing the toxins stored in fat. Others believe that fasting actually slows down the detoxification process by slowing the body's metabolism.
Longer fasts deprive your body of energy, vitamins and minerals that keep our minds and bodies healthy. The immune system suffers during starvation, leaving the body prone to infection.
For healthy adults, short-term fasts of one to two days are unlikely to be harmful, as long as plenty of water or juice is consumed.
Children and teenagers should not fast, except for short periods for religious reasons. Developing bodies and brains need a constant supply of energy to develop properly. Young people should never fast to lose weight.
Dehydration is the greatest danger during a fast. If you do not consume enough fluids, your blood pressure will drop which can cause you to feel weak and possibly faint. Other symptoms are anxiety, pale skin and a rapid heart rate. Humans can survive without fluids for only a few days before death occurs. Dehydration is especially dangerous for infants, children, the elderly and those who live in hot climates.
Some people who fast by taking in water only will develop unpleasant symptoms of hypoglycemia (low blood sugar). They may feel weak, anxious, light-headed, shaky, tired, irritable, hungry and confused. Drinking fruit or vegetable juices regularly to keep the blood sugar level up during a fast can help you avoid these symptoms.
Glucose is the primary fuel for the body. During digestion, all the carbohydrates we eat are broken down into glucose, which is used as the body's energy. It takes about 12 hours for the body to use up all its stored glucose. After this, the body begins breaking down muscle and fat to create enough glucose to fuel the brain and nervous system. After several days, the body adjusts and primarily burns fat for energy, with a smaller amount of muscle loss.
Prolonged fasting obviously leads to weight loss. However, once the fast is over, people usually regain all the weight they lost - and fat is regained more quickly than muscle.
Fasting for a day or two for spiritual reasons is not harmful. Fasting for longer periods, in an attempt to lose weight, detoxify the body or cure a disease is unlikely to be beneficial and could be harmful. A diet of wholesome, natural foods with plenty of fiber and lots of water is the best way to stay healthy.
Kathryn B. Brown is a family nurse practitioner with a master's degree in nursing from OHSU. Is there a health topic you would like to read about? Send your idea to email@example.com.