Fasting is an age-old practice, often done for religious reasons, but fasting for weight loss is still capturing the public imagination. You can find dozens of do-it-yourself plans touting the unproven benefits of fasting, ranging from flushing "poisons" from the body to purging 30 pounds of fat in 30 days. It's true that fasting -- that is, eating little to no food -- will result in weight loss, at least in the short term. But the risks far outweigh any benefits, and ultimately, fasting can cause more harm than good.

Typical Fasting Weight Loss Plans Fasting regimens vary, but the basic premise usually starts with a strict regimen allowing only water, juice and/or some kind of laxative concoction. Some plans allow a few solid foods, but are still called fasts because they provide so few calories. Not all fasts are created equal. Some can be perfectly safe, such as medical fasts supervised by a physician. Religious and cultural fasts are typically undertaken as an act of devotion, last from 24-48 hours, and are not intended to promote weight loss. Fasts lasting a day or two are unlikely to be dangerous for most healthy adults. But high-risk people, the elderly, anyone with a chronic disease, pregnant women, and children are advised against any type of fasting. The real danger lies in staying on the fast for prolonged periods, anywhere from three days to a month.