Metabolism & Nutrient Sensing

Adiponectin is a 30-kDa adipokine secreted predominantly by white adipocytes, with lower expression in brown adipose tissue and trace expression in other tissues such as placenta…

Brown adipose tissue is a thermogenic organ characterized by high mitochondrial density and the expression of uncoupling protein 1 (UCP1), which dissipates the proton gradient…

Caloric restriction is a sustained reduction in energy intake, typically 10–30% below ad libitum, without malnutrition. It activates conserved nutrient-sensing pathways including…

A continuous glucose monitor (CGM) is a wearable sensor, typically inserted into subcutaneous tissue, that measures interstitial glucose every few minutes, typically about 7 to…

CRON is a structured form of caloric restriction in which energy intake is reduced by roughly 20–30% while micronutrient density (vitamins, minerals, essential fatty acids,…

De novo lipogenesis (DNL) is the pathway by which the liver converts excess carbohydrates — primarily glucose and fructose — into fatty acids, packaged as triglycerides into VLDL…

Ectopic fat is lipid stored within or around organs that normally contain little adipose tissue — liver, skeletal muscle, pancreas, heart, and pericardium — distinct from…

The fasting-mimicking diet is a 5-day low-calorie, low-protein, plant-based regimen developed by Valter Longo's group that reproduces metabolic effects of water-only…

Free fatty acids (NEFA, non-esterified fatty acids) are long-chain fatty acids in plasma bound to albumin, released by lipolysis of adipose triglycerides via hormone-sensitive…

Glucagon is a 29-amino-acid peptide hormone secreted by pancreatic alpha-cells in response to hypoglycemia, prolonged fasting, and amino acid ingestion, and suppressed by glucose…

Gluconeogenesis is the metabolic process by which the liver — and, during prolonged fasting, the kidney — synthesizes glucose de novo from non-carbohydrate precursors: primarily…

Glucose variability quantifies the magnitude and frequency of blood glucose fluctuations over hours and days, typically expressed as standard deviation, coefficient of variation,…

HbA1c (glycated hemoglobin) reflects the proportion of hemoglobin stably bound to glucose, providing an integrated estimate of average blood glucose over approximately the prior…

Hepatic insulin resistance describes the selective failure of the liver to suppress gluconeogenesis and glycogenolysis in response to postprandial insulin, while lipogenesis may…

HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) is a fasting blood index calculated as (fasting insulin in µU/mL × fasting glucose in mmol/L) / 22.5, or equivalently…

The incretin effect is the observation that oral glucose ingestion triggers a larger insulin secretory response than an equivalent intravenous glucose infusion — a difference…

Insulin resistance is a state in which target tissues respond poorly to insulin, prompting the pancreas to secrete more to maintain glucose homeostasis. Driven by visceral…

Insulin sensitivity describes how effectively cells, especially in muscle, liver, and adipose tissue, respond to insulin to take up glucose and suppress hepatic glucose output.…

Intermittent fasting is an umbrella term for eating patterns that alternate normal intake with extended fasting windows, including 16:8 time-restricted eating, alternate-day…

The ketogenic diet is a very-low-carbohydrate (typically <50 g/day), high-fat, moderate-protein eating pattern that drives the body into sustained nutritional ketosis. Originally…

Ketone bodies are three water-soluble molecules—β-hydroxybutyrate, acetoacetate, and acetone—produced in hepatocyte mitochondria from acetyl-CoA derived from fatty acid…

Ketosis is a metabolic state in which the liver converts fatty acids into ketone bodies—β-hydroxybutyrate, acetoacetate, and acetone—that serve as alternative fuel for brain,…

Leptin is a 16-kDa adipokine secreted by white adipose tissue in proportion to fat mass; it acts on hypothalamic receptors, particularly in the arcuate nucleus, to suppress…

MASLD (metabolic dysfunction-associated steatotic liver disease) is the 2023 reclassification of what was previously called non-alcoholic fatty liver disease (NAFLD), agreed by…

Metabolic flexibility is the capacity of cells and the whole organism to switch efficiently between fuel sources—primarily glucose and fatty acids—in response to feeding,…

Metabolic syndrome is a cluster of interrelated cardiometabolic risk factors that substantially amplify the risk of type 2 diabetes, cardiovascular disease, and premature…

Postprandial glucose refers to blood glucose levels after a meal, often peaking within 30–90 minutes (typically around 60 minutes for mixed meals) before returning toward fasting…

Prolonged fasting refers to fasting periods of roughly 48 hours up to several days during which only water, electrolytes, and sometimes minimal calories are consumed. After…

The respiratory exchange ratio (RER), synonymous with the respiratory quotient (RQ) under resting and moderate aerobic conditions, is the ratio of carbon dioxide produced (VCO₂)…

Resting metabolic rate (RMR) — sometimes used interchangeably with basal metabolic rate (BMR), though BMR requires stricter fasting and thermoneutral conditions — is the energy…

Time-restricted eating (TRE) confines daily food intake to a consistent window of typically 6–10 hours, leaving 14–18 hours of fasting. The concept emerged from Satchin Panda's…

Uncoupling proteins (UCPs) are carrier proteins in the inner mitochondrial membrane that dissipate the proton electrochemical gradient as heat rather than ATP. UCP1, the…

HOMA-β (Homeostatic Model Assessment of Beta-cell function) is a fasting-state surrogate for pancreatic β-cell insulin-secretory capacity, calculated as (20 × fasting insulin in…

β-oxidation is the principal mitochondrial pathway for catabolizing fatty acids, sequentially cleaving two-carbon acetyl-CoA units from the acyl chain through cycles of…