Intermittent fasting (IF) is a broad term that describes a few different dietary patterns that involve periods of time with an abstinence from food and drink. The most common form of IF is time-restricted eating in which someone consumes all their calories in an 8-hour window, then fasts for 16 hours (this includes sleep). While a 16:8 pattern is most common, there are other variations of time-restricted eating.
Other types of IF include alternate day fasting which is fasting every other day to varying degrees or prolonged fasting which can include a fast mimicking diet or a fast which exceeds 48 hours. Periodic fasting should not be done without guidance and supervision by a physician.
The idea behind intermittent fasting is to abstain from calories long enough that the body must shift from using glucose (sugar) to stored fat as fuel. The shift to using stored fat aids in weight loss.
An exhaustive review of IF by New England Journal of Medicine found that IF has been shown to increase weight loss (1, 2, 3), decrease the incidence of diseases, improve blood sugar regulation, decrease blood pressure, improve blood lipid levels, decrease resting heart rate, increase resistance to stress and suppress inflammation (3).