Wiktionary(1.00 / 1 vote)Rate this definition: quantity(Noun) A fundamental, generic term used when referring to the measurement (count, amount) of a scalar, vector, number of items or to some other way of denominating the value of a collection or group of items. You have to choose between quantity and quality.
When the body is making and using ketones we say that the body is in a state of ketosis. Ketosis begins after about 48 hours (2 days) or water fast for women, or about 72 hours (3 days) of water fast for men.
The Effects of Fasting Ketosis. The process of ketosis is one of the physiological effects of fasting in which the brain (and some other bodily processes) uses ketones produced from fatty tissues as a fuel instead of the usual glucose.