A dietary pattern in which participants eat normally for five days of the week and fast (or severely restrict calories) for two non-consecutive days. 5:2 intermittent fasting induces beneficial metabolic changes due to the shift from carbohydrate metabolism to fatty acid metabolism.

A measure of how sensitive the body's tissues are to the effects of insulin. Insulin sensitivity defines a relationship between insulin production and glucose uptake. Poor insulin sensitivity promotes increased pancreatic insulin production, which can lead to increased risk for high blood pressure, heart disease and heart failure, obesity, osteoporosis, and even cancer.

A broad term that describes periods of voluntary abstention from food and (non-water) drinks, lasting several hours to days. Depending on the length of the fasting period and a variety of other factors, intermittent fasting may promote certain beneficial metabolic processes, such as the increased production of ketones due to the use of stored fat as an energy source. The phrase “intermittent fasting” may refer to any of the following:

• Time-restricted eating
• Alternate-day fasting
• Periodic fasting (multi-day)

Process by which the body switches from using glucose to ketones as the major energy source. Metabolic switching occurs due to changes in gene expression initiated by the restriction of dietary carbohydrates and depletion of the body’s stores of glycogen.

Restricting the timing of food intake to certain hours of the day (typically within an 8- to 12-hour time window that begins with the first food or non-water drink) without an overt attempt to reduce caloric intake. TRE is a type of intermittent fasting. It may trigger some beneficial health effects, such as reduced fat mass, increased lean muscle mass, reduced inflammation, improved heart function with age, increased mitochondrial volume, ketone body production, improved repair processes, and aerobic endurance improvements. Some of these effects still need to be replicated in human trials.