Alternate-day fasting

An eating pattern that alternates fasting or severe calorie restriction on one day with usual eating the next. Fasting-day rules vary, including whether small amounts of food are allowed.

Modified alternate-day fasting: An alternate-day fasting schedule that permits a small amount of food on fasting days. This is the common version that allows roughly 20–25% of daily energy needs on restricted days.
Obesity: A chronic disease characterized by excess adiposity that can impair health. Weight loss is a major reason alternate-day fasting is studied and used.
Time-restricted eating: An eating schedule that confines daily food intake to a recurring time window. It restricts eating within each day rather than alternating restricted and usual-intake days.
Randomized controlled trial: A study that randomly assigns participants to interventions or comparison groups. Randomized trials help distinguish effects of the schedule from differences between participants.
Energy restriction: A sustained reduction in energy intake relative to energy expenditure. Weekly calorie reduction depends on how much intake falls on restricted days and rises on eating days.
Weight loss: A reduction in total body mass over time. Trials compare its weight-loss effects with daily calorie restriction and usual eating.
5:2 diet: An intermittent energy-restriction pattern with two restricted days and five usual-eating days each week. Its two restricted days are not distributed every other day.
Long-term weight maintenance: The sustained prevention of weight regain after weight loss. Short-term weight changes do not establish whether alternate-day fasting is maintainable.
Glycogen: A storage form of glucose found mainly in the liver and skeletal muscle. Fasting depletes liver glycogen, changing the body's short-term fuel supply.
Insulin resistance: A reduced biological response to insulin in target tissues. Researchers assess whether fasting schedules improve markers of glucose regulation.

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Intermittent fastingBroader topic: It applies fasting on alternating days rather than within each day.