Fasting involves total abstinence from food, with only water being drunk. This is a very good way of healing the body because only pure fluids, which do not require much processing, are entering the system, thereby giving the body a complete rest. But fasting should only be considered if you have a lot of experience with cleansing programs.
Detoxification through cleansing involves more than water and can, in many ways, be more effective. It is certainly a more appropriate choice for the majority of people.
Those who are pregnant or breast-feeding should choose only a modified, lighter, and shorter cleansing program using juices, raw foods, and herbs that are acceptable and complementary to pregnancy, along with gentle hydrotherapy. All should be professionally supervised and should not, under any circumstances, include enemas or colonics.
Other people who should avoid fasting programs include those with a sluggish metabolism and congested organs, those already weak and depleted (as fasting can lower the body’s resistance even further), those who are malnourished, those with low blood sugar levels, diabetics, and those contemplating strenuous tasks for their bodies in the near future.
Excessive use of laxatives, colonics, enemas, fasting, and cleansing programs can cause nutritional losses resulting in protein, vitamin, mineral, fat, fiber, and trace-element deficiencies.
Remember, you are aiming to achieve equilibrium in your body, not trauma.
Text Source: The Complete Home Guide to Herbs, Natural Healing, and Nutrition