Is Fasting Safe?
Fasting for a day or two probably won't hurt people who are generally healthy, provided they maintain an adequate fluid intake. However, fasting entirely for long periods of time can be harmful. Your body needs a variety of vitamins, minerals, and other nutrients from food to stay healthy. Not getting enough of these nutrients during fasting diets can lead to symptoms such as fatigue, dizziness, constipation, dehydration, gallstones, and cold intolerance. It is possible to die if you fast too long.
Even short-term fasting is not recommended for people with type I diabetes, because it can lead to dangerous dips and spikes in blood sugar. Women who are pregnant or breastfeeding, or anyone with a chronic disease, should not fast.
Before you go on any type of new diet, particularly one that involves fasting, talk to your doctor to find out whether it is safe and appropriate for you. Also ask your doctor to refer you to a registered dietitian, who can show you how to design a healthy eating plan.