How Safe Is Fasting?

Many people experiment with fasting -- drinking liquids but eating no solid food for one to five days -- for religious, health or medical reasons. Doctors often require you to fast for several hours before surgery or certain medical tests, and some popular diets, such as the Master Cleanse diet and the Hollywood Diet, utilize fasting to help you drop weight more quickly. Although an occasional short-term fast probably will not harm your overall health, fasting on a regular basis can deprive your body of the important nutrients, vitamins and minerals that it needs to function properly.

Short-Term Effects

Failing to eat regularly can make you irritable and tired. This fatigue can make you reluctant to engage in physical activity and even interfere with your day-to-day activities. Other possible side effects include dizziness, headaches and abnormal heart rhythms. Extreme hunger can make it hard to focus and can cause emotional distress. Fasting accompanied by rapid weight loss can impair your immune system, according to the American Council on Exercise. A lowered immune system can make you more vulnerable to colds, flu and other illnesses.

Long-Term Effects

Depriving your body of the right nutrients can cause malnutrition, which can do lasting damage to your heart, liver, kidneys and other organs. Going without food on a regular basis can stunt children's growth, which can make them shorter than average. In extreme cases, fasting can result in death by starvation. The American Cancer Society recommends that pregnant or breastfeeding women, and people with serious health issues, such as advanced forms of cancer, avoid fasting.

Considerations

Fasting for weight loss feeds the cycle of yo-yo dieting that can make it hard for you to achieve a healthy body weight. Ruth Frechman, a registered dietitian in Burbank, California, and spokesperson for the American Dietetic Association, tells the "Los Angeles Times" that fasting as a dieting strategy can backfire and result in weight gain. According to Frechman, many people overeat the day after the fast to compensate for their extreme hunger. Any pounds you do manage to lose are primarily due to water loss. When you start to eat or drink normally, all of the weight piles right back on.

Misconceptions

Although some people believe that fasting "cleans out" your system by removing toxins, it actually can cause toxic chemicals to build up in your body. The American Dietetic Association explains that body chemicals called ketones collect in your system when you do not have adequate carbohydrate stores. Your kidneys must then work extra hard to eliminate the ketones.