Fasting has also been noted to trigger an early period of rapid weight loss, often averaging one to two pounds per day for the first few days. This isn’t, unfortunately, due to loss of body fat. Fat loss during fasting averages approximately ½ pound per day. If you are losing 1 pound or more a day, the excess above ½ pound is water weight and will rapidly be regained upon eating. This is not abnormal or unusual. Don’t be disappointed when the water weight returns or decide that fasting doesn’t work.