Latin for "at one's pleasure" or "as you desire." In biology, this term is used to describe "free feeding."

An intracellular degradation system involved in the disassembly and recycling of unnecessary or dysfunctional cellular components. Autophagy participates in cell death, a process known as autophagic dell death. Prolonged fasting is a robust initiator of autophagy and may help protect against cancer and even aging by reducing the burden of abnormal cells.

The relationship between autophagy and cancer is complex, however. Autophagy may prevent the survival of pre-malignant cells, but can also be hijacked as a malignant adaptation by cancer, providing a useful means to scavenge resources needed for further growth.

A chemical produced in the liver via the breakdown of fatty acids. Beta-hydroxybutyrate is a type of ketone body. It can be used to produce energy inside the mitochondria and acts as a signaling molecule that alters gene expression by inhibiting a class of enzymes known as histone deacetylases.

A type of protein that acts on neurons in the central and peripheral nervous systems. BDNF is a type of neurotrophin – or growth factor – that controls and promotes the growth of new neurons. It is active in the hippocampus, cortex, cerebellum, and basal forebrain – areas involved in learning, long term memory, and executive function. Rodent studies suggest that lactate, one of many so-called exerkines, mediates some of the benefits of exercise on learning and memory via inducing neuronal BDNF expression.^[1] Exercise in combination with heat stress increases BDNF more effectively than exercise alone.^[2] BDNF is a profoundly universal point of convergence for mechanistically explaining essentially all known activities that promote brain health.

A peptide hormone secreted by the beta cells of the pancreatic islets cells. Insulin maintains normal blood glucose levels by facilitating the uptake of glucose into cells; regulating carbohydrate, lipid, and protein metabolism; and promoting cell division and growth. Insulin resistance, a characteristic of type 2 diabetes, is a condition in which normal insulin levels do not produce a biological response, which can lead to high blood glucose levels.

A physiological condition in which cells fail to respond to the normal functions of the hormone insulin. During insulin resistance, the pancreas produces insulin, but the cells in the body become resistant to its actions and are unable to use it as effectively, leading to high blood sugar. Beta cells in the pancreas subsequently increase their production of insulin, further contributing to a high blood insulin level.

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)

Molecules (often simply called “ketones”) produced by the liver during the breakdown of fatty acids. Ketone production occurs during periods of low food intake (fasting), carbohydrate restrictive diets, starvation, or prolonged intense exercise. There are three types of ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone. Ketone bodies are readily used as energy by a diverse array of cell types, including neurons.

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.

A cluster of at least three of five of the following medical conditions: abdominal (central) obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides, and low high-density lipoprotein (HDL) levels. Some studies estimate the prevalence in the USA to be 34 percent of the adult population. Metabolic syndrome is associated with the risk of developing cardiovascular disease and diabetes.

Oxygen-containing chemically-reactive molecules generated by oxidative phosphorylation and immune activation. ROS can damage cellular components, including lipids, proteins, mitochondria, and DNA. Examples of ROS include: peroxides, superoxide, hydroxyl radical, and singlet oxygen.

A related byproduct, reactive nitrogen species, is also produced naturally by the immune system. Examples of RNS include nitric oxide, peroxynitrite, and nitrogen dioxide.

The two species are often collectively referred to as ROS/RNS. Preventing and efficiently repairing damage from ROS (oxidative stress) and RNS (nitrosative stress) are among the key challenges our cells face in their fight against diseases of aging, including cancer.

A metabolic disorder characterized by high blood sugar and insulin resistance. Type 2 diabetes is a progressive condition and is typically associated with overweight and low physical activity. Common symptoms include increased thirst, frequent urination, unexplained weight loss, increased hunger, fatigue, and impaired healing. Long-term complications from poorly controlled type 2 diabetes include heart disease, stroke, diabetic retinopathy (and subsequent blindness), kidney failure, and diminished peripheral blood flow which may lead to amputations.