Nutrition Glossary

Anabolic Window

The now-debunked idea that you must consume protein within 30 minutes of exercise to maximize muscle growth. Research shows the window is actually 1-2 hours, and total daily protein intake matters far more than timing.

Autophagy

A cellular cleanup process where cells degrade and recycle damaged components. Some research suggests intermittent fasting may enhance autophagy, though human evidence is still preliminary.

Basal Metabolic Rate (BMR)

The number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, and cell production. BMR accounts for 60-75% of total daily energy expenditure.

Related: TDEE, Mifflin-St Jeor Equation

Body Mass Index (BMI)

A screening metric calculated as weight (kg) / height (m)². BMI correlates with body fat in populations but cannot distinguish muscle from fat at the individual level.

Related: Body Fat Percentage, FFMI

Casein Protein

A slow-digesting milk protein that provides a sustained release of amino acids over 5-7 hours. Taking 30-40g of casein before bed can increase overnight muscle protein synthesis by ~22%.

Complete Protein

A protein source containing all nine essential amino acids in adequate amounts. Animal proteins (meat, dairy, eggs) are naturally complete. Most plant proteins are incomplete, except soy, quinoa, and hemp.

EAA (Essential Amino Acids)

The 9 amino acids your body cannot produce: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. They must come from food. Complete proteins contain all 9 in adequate amounts.

Electrolytes

Minerals that carry an electric charge and are essential for hydration, nerve function, and muscle contraction: sodium, potassium, chloride, calcium, magnesium, and phosphate. Sweating depletes sodium and potassium most significantly.

FFMI (Fat-Free Mass Index)

A height-normalized measure of lean body mass. FFMI = fat-free mass (kg) / height (m)². The natural limit for men is approximately 25 (26.5 adjusted). Values above 26 in men suggest PED use.

Glycemic Index (GI)

A scale from 0-100 that ranks carbohydrate-containing foods by how quickly they raise blood sugar. Pure glucose has a GI of 100. Foods below 55 are considered low-GI.

Insulin Resistance

A condition where cells become less responsive to insulin, causing the pancreas to produce more. Over time, this can lead to prediabetes and type 2 diabetes. Strongly linked to visceral fat, physical inactivity, and ultra-processed food consumption.

Ketosis

A metabolic state where your body primarily burns ketones (from fat) instead of glucose (from carbs) for fuel. Typically achieved by consuming fewer than 50g of carbohydrates per day.

Leucine

An essential branched-chain amino acid (BCAA) and the main trigger for muscle protein synthesis. A meal needs approximately 2-3g of leucine to maximally stimulate muscle building.

Macronutrients

The three nutrients your body needs in large amounts: protein (4 cal/g), carbohydrates (4 cal/g), and fat (9 cal/g). Alcohol provides 7 cal/g but is not considered a macronutrient.

Metabolic Adaptation

The decrease in metabolic rate that occurs during calorie restriction, beyond what would be expected from weight loss alone. Your body "fights back" against dieting by reducing BMR by 5-15%, increasing hunger hormones, and decreasing NEAT.

Micronutrients

Vitamins and minerals required in small amounts for proper bodily function. Unlike macronutrients, micronutrients do not provide calories but are essential for thousands of biochemical reactions.

Mifflin-St Jeor Equation

The most accurate predictive formula for estimating BMR, published in 1990. Men: BMR = 10×kg + 6.25×cm - 5×age + 5. Women: BMR = 10×kg + 6.25×cm - 5×age - 161.

NEAT (Non-Exercise Activity Thermogenesis)

Calories burned through daily activities that aren't structured exercise: fidgeting, walking, standing, household chores. NEAT can vary by up to 2,000 calories per day between individuals and is a major factor in weight management.

NOVA Classification

A system that categorizes foods into 4 groups based on processing level: (1) unprocessed/minimally processed, (2) processed culinary ingredients, (3) processed foods, (4) ultra-processed foods. The 2025 Dietary Guidelines emphasize limiting Group 4.

Omega-3 Fatty Acids

Essential polyunsaturated fats (EPA, DHA, ALA) that your body cannot produce. EPA and DHA (from marine sources) are anti-inflammatory and critical for brain and heart health. ALA (from plants) converts to EPA/DHA poorly (5-10%).

Prebiotics

Types of dietary fiber that feed beneficial gut bacteria. Top sources include inulin (Jerusalem artichokes, garlic, onions), resistant starch (cooled potatoes, oats), and beta-glucan (oats, barley).

Probiotics

Live beneficial bacteria found in fermented foods (yogurt, kefir, sauerkraut, kimchi, kombucha) and supplements. They temporarily colonize the gut and may improve digestive health, immune function, and inflammation.

RDA (Recommended Dietary Allowance)

The daily intake level sufficient to meet the requirements of 97.5% of healthy individuals. For protein, the RDA is 0.8 g/kg, the minimum to prevent deficiency, not the optimal intake for health or performance.

Sarcopenia

Age-related loss of muscle mass and strength. Adults lose 3-8% of muscle mass per decade after age 30, accelerating after 60. Resistance training and adequate protein (1.2-1.6 g/kg) are the most effective interventions.

Thermic Effect of Food (TEF)

The energy your body expends digesting, absorbing, and metabolizing food. TEF accounts for about 10% of total daily energy expenditure. Protein has the highest TEF (20-30%), followed by carbs (5-10%) and fat (0-3%).

Total Daily Energy Expenditure (TDEE)

The total number of calories your body burns in 24 hours, including BMR, the thermic effect of food, and all physical activity. TDEE = BMR × activity multiplier.

Related: BMR, Activity Multiplier

Ultra-Processed Foods (UPF)

Industrial formulations made mostly from substances extracted from foods, with additives like preservatives, emulsifiers, and artificial flavors. Linked to overeating, obesity, and chronic disease. The 2025 Dietary Guidelines recommend limiting UPFs.

Visceral Fat

Fat stored deep inside the abdomen around internal organs. Unlike subcutaneous fat (under the skin), visceral fat is metabolically active and strongly linked to insulin resistance, type 2 diabetes, and cardiovascular disease.

Whey Protein

A fast-absorbing milk protein with the highest biological value of any protein source. Whey is 11% leucine, making it ideal for post-workout muscle protein synthesis. Two forms: concentrate (70-80% protein) and isolate (90%+ protein).

A1C (Hemoglobin A1C)

A measure of average blood glucose over the past 2-3 months. Glucose attaches to hemoglobin in red blood cells, which live about 120 days. A1C below 5.7% is normal; 5.7-6.4% is prediabetes; ≥6.5% meets the diagnostic threshold for diabetes. The ADA treatment target for most adults with diabetes is below 7.0%.

Related: eAG, HOMA-IR, Insulin Resistance

Apolipoprotein B (ApoB)

A protein on every atherogenic lipoprotein particle (LDL, VLDL, IDL, Lp(a)). Measuring ApoB counts the actual number of plaque-forming particles, which can be more predictive of cardiovascular risk than LDL cholesterol, especially in people with metabolic syndrome or low LDL but high particle count. Emerging as a primary target alongside LDL.

ASCVD (Atherosclerotic Cardiovascular Disease)

The umbrella term for plaque-driven cardiovascular disease: heart attack, stroke, and peripheral arterial disease. The ACC/AHA Pooled Cohort Equations estimate 10-year ASCVD risk to guide statin and BP therapy decisions. A risk of 7.5% or higher generally warrants a moderate-intensity statin.

Related: CAC Score, LDL Cholesterol

Beta-Hydroxybutyrate (BHB)

The most abundant ketone body produced during fasting or ketogenic eating. BHB crosses the blood-brain barrier to fuel the brain and signals anti-inflammatory and epigenetic pathways. Blood BHB above 0.5 mM indicates nutritional ketosis; 1.5-3.0 mM is the optimal range for most therapeutic keto protocols.

Related: Ketosis

Caffeine

The most consumed psychoactive compound worldwide. Blocks adenosine receptors to delay fatigue and improve alertness. Average half-life is 5 hours (range 2-12 by CYP1A2 genetics). FDA safe limit is 400 mg/day for adults; ACOG recommends <200 mg/day in pregnancy; AAP advises against caffeine in children and adolescents.

Coronary Artery Calcium (CAC) Score

A non-contrast CT scan that quantifies calcified plaque in the coronary arteries. CAC of 0 typically argues for withholding statin; CAC 1-99 favors statin; CAC ≥100 strongly favors statin, especially in borderline ASCVD risk (5-20%). Powerful tool for shared decision-making in primary prevention.

Related: ASCVD, LDL Cholesterol

Creatine Monohydrate

The most studied sports supplement in history. Raises muscle phosphocreatine by 10-40%, extending maximal-effort work and increasing training volume. Standard dose: 3-5 g/day ongoing (or 20 g/day for 5-7 days loading then 3-5 g/day). 30+ years of safety data. Recent trials show cognitive benefits at 5 g/day.

DASH Diet

Dietary Approaches to Stop Hypertension, a diet rich in fruits, vegetables, whole grains, low-fat dairy, and lean protein, low in saturated fat, sodium, and added sugar. Proven to lower systolic BP by 8-14 mmHg in 8 weeks. Combined with sodium restriction (<1,500 mg/day), the effect rivals a single BP medication.

Related: Mediterranean Diet, Sodium

eGFR (Estimated Glomerular Filtration Rate)

An estimate of how well the kidneys filter blood, calculated from serum creatinine, age, and sex using the 2021 race-free CKD-EPI equation. Normal is ≥90 mL/min/1.73m². 60-89 is mildly reduced; 45-59 moderate (G3a); 30-44 moderate-severe (G3b); 15-29 severe (G4); <15 kidney failure (G5). Used for CKD staging and drug dosing.

Related: A1C (Hemoglobin A1C)

Estimated Average Glucose (eAG)

The translation of A1C into the same mg/dL units used on home glucose meters. Derived from the ADAG study: eAG (mg/dL) = 28.7 × A1C − 46.7. A1C of 7% corresponds to eAG of 154 mg/dL; A1C of 8% to 183 mg/dL. Helps patients understand what an A1C result means day to day.

Related: A1C (Hemoglobin A1C)

FODMAP

Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols, short-chain carbohydrates poorly absorbed in the small intestine. A low-FODMAP diet is the most evidence-based dietary therapy for irritable bowel syndrome (IBS), reducing symptoms in 50-80% of patients. The diet is implemented in three phases: elimination, reintroduction, personalization.

GLP-1 Receptor Agonists

A class of medications (semaglutide, liraglutide, tirzepatide) that mimic the GLP-1 hormone, slowing gastric emptying, increasing satiety, and improving insulin secretion. Originally developed for type 2 diabetes, they produce 10-20% weight loss and are now first-line pharmacotherapy for obesity. Also reduce cardiovascular events in high-risk patients.

Glycemic Load (GL)

A more accurate predictor of blood sugar response than glycemic index alone. Calculated as GL = (GI × grams of carbohydrate per serving) / 100. Under 10 is low impact, 10-19 medium, 20+ high. A daily total under 100 is associated with stable blood sugar and lower diabetes risk.

Related: Glycemic Index (GI)

HDL Cholesterol

High-density lipoprotein, the 'good' cholesterol that removes cholesterol from arteries and transports it to the liver for disposal. Higher HDL is generally protective (target ≥40 mg/dL in men, ≥50 in women), though extremely high HDL from genetics is not always beneficial. Raised by aerobic exercise, omega-3, and moderate alcohol; lowered by smoking and trans fat.

HOMA-IR

Homeostatic Model Assessment of Insulin Resistance, estimates insulin resistance from a single fasting blood draw of glucose and insulin: HOMA-IR = (fasting glucose in mmol/L × fasting insulin in µIU/mL) / 22.5. Under 1.0 is excellent, 1.0-1.9 healthy, 1.9-2.9 early insulin resistance, 2.9+ significant IR. Most useful in prediabetes and metabolic syndrome.

LDL Cholesterol

Low-density lipoprotein, the primary driver of atherosclerotic plaque and the main target of statin therapy. Treatment targets: <100 mg/dL for low risk, <70 for moderate risk, <55 for very high risk. Lowered by reducing saturated fat, adding soluble fiber, plant sterols, and (when needed) statins or PCSK9 inhibitors. Each 1 mmol/L (39 mg/dL) LDL reduction cuts cardiovascular events by ~22%.

Lipoprotein(a)

A genetically-determined LDL variant with an attached apolipoprotein(a) that promotes clotting and inflammation. Elevated Lp(a), affecting ~20% of people, increases cardiovascular risk 2-4× independently of other lipids. Standard lipid panels don't measure Lp(a); a one-time test is recommended at least once in every adult's lifetime.

Mediterranean Diet

An eating pattern inspired by traditional Greek, southern Italian, and Spanish cuisine: olive oil, vegetables, fruits, legumes, whole grains, nuts, fish, moderate wine, low red meat. The PREDIMED trial showed a 30% reduction in major cardiovascular events. ADA, AHA, and Dietary Guidelines all rank it among the healthiest eating patterns.

Related: DASH Diet, MIND Diet

Metabolic Syndrome

A cluster of cardiometabolic risk factors: abdominal obesity (waist ≥40 in men, ≥35 in women), elevated triglycerides (≥150 mg/dL), low HDL (<40 M, <50 F), elevated BP (≥130/85), and elevated fasting glucose (≥100 mg/dL). Three of five meets the diagnosis. Affects ~35% of U.S. adults and drives most type 2 diabetes and cardiovascular disease.

MIND Diet

Mediterranean-DASH Intervention for Neurodegenerative Delay, a hybrid of the Mediterranean and DASH diets emphasizing berries, leafy greens, nuts, olive oil, whole grains, fish, beans, poultry, and wine, while limiting red meat, butter, cheese, pastries, and fried food. Adherence is associated with slower cognitive decline and lower Alzheimer's risk.

NAFLD (Non-Alcoholic Fatty Liver Disease)

Now called MAFLD (Metabolic dysfunction-Associated Fatty Liver Disease). Fat accumulation in the liver not caused by alcohol, affects ~25% of adults and >70% of those with type 2 diabetes. Driven by insulin resistance, fructose, and ultra-processed food. Reversible with 5-10% weight loss; can progress to NASH, cirrhosis, and liver cancer if untreated.

Non-HDL Cholesterol

Total cholesterol minus HDL, captures every atherogenic particle (LDL, VLDL, IDL, Lp(a)). The 2018 ACC/AHA guidelines set a non-HDL target of 30 mg/dL above the LDL goal (typically <130 mg/dL for higher-risk patients). Especially useful when triglycerides are >200 mg/dL because LDL calculations become less accurate in that setting.

Related: LDL Cholesterol, HDL Cholesterol

Nutrigenomics

The study of how individual genetic variation affects response to nutrients. Variants like MTHFR (folate), APOE4 (saturated fat response), LCT (lactose tolerance), and CYP1A2 (caffeine metabolism) explain why the same diet affects people differently. Still emerging in clinical practice, with direct-to-consumer testing now widely available.

Omega-6 Fatty Acids

Polyunsaturated fats essential for health (the body cannot make them). Linoleic acid (from seed oils, nuts, seeds) is the most common. The omega-6:omega-3 ratio in modern diets is often 15:1, far above the historical 4:1. Most recent evidence suggests omega-6 does not promote inflammation at typical intakes; reducing added sugar and ultra-processed food matters more.

Phytochemicals

Bioactive compounds produced by plants (polyphenols, flavonoids, carotenoids, glucosinolates) that are not essential but appear to reduce inflammation, oxidative stress, and cancer risk. Found in colorful fruits and vegetables, herbs, spices, tea, coffee, and dark chocolate. A 'food first' approach is preferred, supplements of isolated phytochemicals have generally disappointed in trials.

Polyphenols

The largest class of phytochemicals, over 8,000 identified. Subclasses include flavonoids (berries, citrus, cocoa), phenolic acids (coffee, whole grains), and stilbenes (red wine resveratrol). Polyphenol-rich diets are associated with lower cardiovascular, cancer, and cognitive decline risk. Extra-virgin olive oil, berries, and dark chocolate are concentrated sources.

Pulse Pressure

Systolic blood pressure minus diastolic. A wide pulse pressure (above 60 mmHg) is common in older adults and signals arterial stiffening, an independent predictor of cardiovascular events. Reflects reduced elasticity of the aorta and major arteries. Typically widens with age and uncontrolled hypertension.

Resistant Starch

A type of starch that resists digestion in the small intestine and reaches the colon, where it feeds beneficial bacteria and produces short-chain fatty acids (especially butyrate). Found in cooled cooked potatoes, green bananas, oats, legumes. Increases satiety, improves insulin sensitivity, and may lower colon cancer risk. ~15-20 g/day is a reasonable target.

Satiety Index

A measure of how effectively a food satisfies hunger, developed by Susanna Holt at the University of Sydney in 1995. White bread = 100. Boiled potatoes score 323 (most satiating); croissants score 47 (least). High-protein, high-fiber, high-water foods generally score highest. Useful for designing meals that control hunger on a calorie deficit.

Saturated Fat

A type of dietary fat with no double bonds in the carbon chain, solid at room temperature. Found in meat, dairy, tropical oils (coconut, palm). The Dietary Guidelines recommend limiting to <10% of calories, but the source matters: dairy saturated fat appears less harmful than processed meat saturated fat. Replacing saturated with unsaturated fat lowers cardiovascular risk.

Statins

HMG-CoA reductase inhibitors (atorvastatin, rosuvastatin, simvastatin) that lower LDL cholesterol by 30-60% and reduce cardiovascular events by ~25% per 1 mmol/L LDL reduction. Recommended for most adults with ASCVD risk ≥7.5%, LDL ≥190, established cardiovascular disease, or diabetes with additional risk factors. Generally well-tolerated; ~5-10% experience muscle symptoms.

Time-Restricted Eating (TRE)

A form of intermittent fasting that compresses daily food intake into a window of typically 4-12 hours, with the rest of the day spent fasting. 16:8 (12pm-8pm) is most common. TRE improves insulin sensitivity, lowers post-prandial glucose, and may aid weight loss via spontaneous calorie reduction. Effects on autophagy are still being studied in humans.

Trans Fat

Unsaturated fat with at least one trans double bond. Artificial trans fats (partially hydrogenated oils) were banned in the U.S. in 2018 because they raise LDL, lower HDL, and increase cardiovascular disease by ~30% at intakes of just 2% of calories. Small amounts of natural trans fats occur in ruminant meat and dairy but appear less harmful.

Triglycerides

The main storage form of fat in the body and the main fat type in the bloodstream after meals. Fasting triglycerides <150 mg/dL is normal; 150-199 borderline; 200-499 high; ≥500 very high. Driven by refined carbs, alcohol, sedentary lifestyle, and uncontrolled diabetes. Lowered by reducing sugar and alcohol, increasing omega-3, and aerobic exercise.

VO2 Max

The maximum rate of oxygen consumption during incremental exercise, the gold-standard measure of cardiorespiratory fitness. Measured in mL/kg/min or METs. Elite endurance athletes exceed 70 mL/kg/min; sedentary adults average 30-40. Each 3.5 mL/kg/min (1 MET) increase is associated with ~10-15% lower all-cause mortality. Improved by sustained aerobic training, especially intervals.

Omega-3 Index

The percentage of EPA + DHA in red blood cell membranes, a stable biomarker of long-chain omega-3 status. Index of 8-12% is associated with lowest cardiovascular risk; below 4% is high risk. A more reliable measure than a single plasma reading. Raised by eating fatty fish 2×/week or taking 1-2 g/day of EPA+DHA. Targets may be higher (12%) for cognitive benefits.

Biological Value (BV)

A measure of how much absorbed nitrogen from a protein is retained by the body for growth and maintenance. Whole eggs top the scale at 100, with whey close behind, while wheat and legumes score much lower. The metric has largely been replaced by PDCAAS and DIAAS in modern nutrition research.

Related: PDCAAS, DIAAS, Complete Protein

PDCAAS (Protein Digestibility Corrected Amino Acid Score)

The Protein Digestibility Corrected Amino Acid Score, adopted by the FDA and FAO/WHO in 1989 as the standard for assessing protein quality. It evaluates amino acid content against preschool-aged child requirements, then corrects for digestibility. Scores max out at 1.0, which is why milk, eggs, whey, and soy all appear equally perfect despite real differences in bioavailability.

Related: DIAAS, Biological Value (BV)

DIAAS (Digestible Indispensable Amino Acid Score)

The Digestible Indispensable Amino Acid Score, recommended by the FAO in 2013 as a successor to PDCAAS. Unlike its predecessor, DIAAS measures amino acid digestibility at the end of the small intestine (ileal digestibility) rather than in the feces, and it allows scores above 100%, revealing real quality differences between animal and plant proteins. Milk protein concentrates and whey often score above 1.0, while most plant proteins fall between 0.5 and 0.7.

Related: PDCAAS, Biological Value (BV)

Net Carbs

Total carbohydrates minus dietary fiber and sugar alcohols, a label popular on low-carb products. The concept assumes that fiber and most sugar alcohols do not spike blood glucose because they are not fully absorbed. The FDA does not formally define or regulate the term, so companies calculate it inconsistently.

Related: Glycemic Index (GI), Glycemic Load (GL)

Glycogen

The storage form of carbohydrate in the body, found primarily in skeletal muscle and the liver. Total body capacity is roughly 500 grams (about 2,000 calories), with muscle glycogen fueling activity and liver glycogen maintaining blood glucose between meals. Carbohydrate loading before endurance events and the keto flu during very low-carb transitions both reflect glycogen dynamics.

Branched-Chain Amino Acids (BCAAs)

The three essential amino acids leucine, isoleucine, and valine, named for their branched molecular structure. Leucine is the primary trigger for muscle protein synthesis, with a threshold of about 2 to 3 grams per meal. Supplementing BCAAs alone provides little benefit if total daily protein is adequate, since intact protein sources supply them along with the other essential amino acids needed for complete synthesis.

Related: Leucine, EAA (Essential Amino Acids), Whey Protein

Soluble Fiber

A type of dietary fiber that dissolves in water to form a viscous gel, slowing digestion and blunting post-meal glucose spikes. Found in oats, barley, legumes, psyllium, and the flesh of fruits, it also lowers LDL cholesterol by binding bile acids in the gut. The FDA recognizes a health claim that 3 grams per day of soluble fiber from oats can reduce coronary heart disease risk.

Related: Resistant Starch, Prebiotics

Insoluble Fiber

Dietary fiber that does not dissolve in water, adding bulk to stool and speeding transit through the colon. Wheat bran, whole grains, and the skins of many vegetables are concentrated sources. Although it is less metabolically active than soluble fiber, insoluble fiber is associated with lower rates of constipation and diverticular disease.

Related: Soluble Fiber, Resistant Starch

Bioavailability

The proportion of a nutrient that is absorbed from the digestive tract and made available for use or storage. Bioavailability varies widely: heme iron from meat is absorbed at 15 to 35%, while non-heme iron from plants typically absorbs at only 2 to 20%. Vitamin C, cooking methods, and compounds like phytates and oxalates all shift the numbers significantly.

Related: Phytates (Phytic Acid), Oxalates

Phytates (Phytic Acid)

Storage compounds of phosphorus found in the bran of whole grains, legumes, nuts, and seeds. They chelate minerals such as iron, zinc, calcium, and magnesium, reducing absorption by 50% or more in some cases. Soaking, sprouting, fermentation, and vitamin C can mitigate the effect, which is one reason traditional cultures often process grains before eating them.

Related: Oxalates, Bioavailability, Tannins

Oxalates

Naturally occurring compounds in spinach, rhubarb, beets, almonds, and dark chocolate that bind calcium and other minerals in the gut. Most people excrete oxalate without issue, but those with a history of calcium oxalate kidney stones may be advised to limit high-oxalate foods and ensure adequate calcium intake at meals. Boiling can reduce oxalate content in vegetables by 30 to 87%.

Related: Phytates (Phytic Acid), Bioavailability

Lecithin

A phospholipid found in egg yolks, soybeans, and sunflower seeds that acts as a natural emulsifier, allowing fat and water to mix. It is also a concentrated source of choline, an essential nutrient involved in acetylcholine synthesis, cell membrane integrity, and lipid transport. Most people get enough lecithin from food, though it is widely added to processed foods as soy lecithin to improve texture.

Related: Choline, Emulsification

Carotenoids

A family of more than 600 fat-soluble plant pigments responsible for the red, orange, and yellow colors of many fruits and vegetables. About 50 have provitamin A activity, with beta-carotene being the best known, while lutein, zeaxanthin, and lycopene function as antioxidants without converting to vitamin A. Absorption improves significantly when eaten with a source of dietary fat.

Related: Bioavailability, Polyphenols

Glucosinolates

Sulfur-containing compounds found in cruciferous vegetables like broccoli, Brussels sprouts, cabbage, and kale. When these vegetables are chopped or chewed, the enzyme myrosinase converts glucosinolates into isothiocyanates such as sulforaphane, which have shown anti-cancer and anti-inflammatory activity in cell and animal studies. Light steaming preserves the enzyme, while prolonged boiling destroys it.

Related: Polyphenols, Phytochemicals

Lignans

A class of polyphenolic phytoestrogens concentrated in flaxseed, sesame seeds, and whole grains. Gut bacteria convert them into enterolignans, which can weakly bind estrogen receptors and may modestly influence hormone-related conditions. Flaxseed at 1 to 2 tablespoons per day is the most studied dietary source, with research suggesting benefits for cholesterol and menopausal symptoms.

Related: Polyphenols, Phytochemicals

Saponins

Bitter, soap-like compounds produced by plants including legumes, quinoa, ginseng, and licorice root. They get their name from their tendency to form a soapy foam when shaken in water, and some have been shown to lower cholesterol by binding bile acids. While generally safe at dietary levels, very high doses can irritate the gut, which is why quinoa is traditionally rinsed before cooking.

Related: Phytates (Phytic Acid), Tannins

Tannins

Astringent polyphenols found in tea, red wine, coffee, dark chocolate, and unripe fruits that can bind iron and proteins. They are responsible for the dry mouthfeel of strong black tea or young red wine and can reduce non-heme iron absorption by up to 60% when consumed at the same meal. Drinking tea between meals rather than with them is a common strategy for people at risk of iron deficiency.

Related: Phytates (Phytic Acid), Polyphenols, Bioavailability

Choline

An essential nutrient recognized by the Institute of Medicine in 1998, needed for acetylcholine synthesis, phospholipid formation, and one-carbon metabolism. Eggs are the richest source, with one large egg providing about 147 mg of the 550 mg adult Adequate Intake. Most Americans fall short of recommended intake, and deficiency can cause fatty liver and muscle damage in severe cases.

Related: Lecithin

EPOC (Excess Post-exercise Oxygen Consumption)

The elevated oxygen uptake, and calorie burn, that continues for hours after intense exercise as the body restores ATP, clears lactate, replenishes glycogen, and repairs tissue. The effect is real but modest, typically adding 6 to 15% of the calories burned during the workout itself. High-intensity interval training and heavy resistance training produce larger EPOC than steady-state cardio, but not enough to offset a poor diet.

Related: Thermic Effect of Food (TEF), NEAT (Non-Exercise Activity Thermogenesis), Total Daily Energy Expenditure (TDEE)

Gluconeogenesis

The metabolic pathway, primarily in the liver and to a lesser extent the kidney, that synthesizes glucose from non-carbohydrate precursors like lactate, glycerol, and certain amino acids. It becomes a major glucose source during fasting, very low-carb diets, and prolonged exercise, supplying the brain and red blood cells that depend on glucose. The process is upregulated by glucagon and cortisol, and suppressed by insulin.

Related: Ketosis, Glycogen, Lipolysis

Lipolysis

The breakdown of stored triglycerides in adipose tissue into free fatty acids and glycerol, which can then be used for energy by most tissues. It is stimulated by catecholamines, glucagon, and growth hormone, and suppressed by insulin, which is why high insulin levels make fat loss difficult. The liberated fatty acids travel bound to albumin to muscles and the liver, where they undergo beta-oxidation.

Related: Ketosis, Gluconeogenesis, Beta-Hydroxybutyrate (BHB)

Insulin Sensitivity

How responsive target tissues, especially muscle, liver, and fat, are to a given amount of insulin. Higher sensitivity means cells take up glucose efficiently at lower insulin levels, while low sensitivity, called insulin resistance, forces the pancreas to secrete more. Regular resistance and aerobic training, adequate sleep, weight loss, and reduced intake of added sugars all improve insulin sensitivity.

Related: Insulin Resistance, HOMA-IR, A1C (Hemoglobin A1C)

Ghrelin

A peptide hormone produced mainly by the stomach that rises before meals and falls after eating, signaling hunger to the brain. Ghrelin also stimulates growth hormone release and shifts food preference toward calorie-dense foods. During weight loss, ghrelin tends to rise, which is one biological reason long-term weight maintenance is difficult.

Related: Leptin, Satiety Index

Leptin

A hormone secreted by fat cells that communicates long-term energy stores to the hypothalamus and suppresses appetite. Blood levels correlate with body fat percentage, so obesity is associated with high leptin, but the brain stops responding effectively, a state known as leptin resistance. During caloric restriction, leptin drops faster than fat mass, contributing to the increased hunger of dieting.

Related: Ghrelin, Insulin Sensitivity

AMPK (AMP-activated protein kinase)

An energy-sensing enzyme that acts as a master switch for cellular metabolism. When ATP is depleted relative to AMP, as during exercise, fasting, or caloric restriction, AMPK activates pathways that increase fat oxidation and glucose uptake while turning off energy-intensive processes like fat and protein synthesis. Metformin, berberine, and resveratrol all act partly through AMPK activation.

Related: mTOR (mechanistic target of rapamycin), Autophagy

mTOR (mechanistic target of rapamycin)

A nutrient-sensing kinase that integrates signals from amino acids, insulin, energy status, and growth factors to drive cell growth and protein synthesis. mTORC1, the better-studied complex, is activated by leucine and other amino acids and suppressed by fasting, caloric restriction, and rapamycin. Chronic overactivation, common in obesity, is linked to accelerated aging and cancer risk, which is one argument for periodic fasting.

Related: AMPK (AMP-activated protein kinase), Autophagy, Leucine

Ketogenic Diet

A very low-carbohydrate, high-fat eating pattern, typically 20 to 50 grams of carbs per day, designed to induce and maintain ketosis. Originally developed in the 1920s to treat drug-resistant epilepsy in children, it has since been studied for weight loss, type 2 diabetes, and metabolic syndrome. Long-term adherence is challenging, and the diet requires attention to micronutrients, fiber, and hydration to avoid common side effects.

Related: Ketosis, Beta-Hydroxybutyrate (BHB), Time-Restricted Eating (TRE)

Carnivore Diet

An elimination-style eating pattern consisting exclusively of animal foods, including meat, fish, eggs, and sometimes dairy, with all plant foods excluded. Proponents report improvements in digestion and autoimmune symptoms, but there are no published long-term clinical trials, and the diet is low in fiber, vitamin C, and several phytochemicals. Most nutrition authorities consider it nutritionally incomplete without careful planning or supplementation.

Related: Ketogenic Diet, Ketosis

Dietary Inflammatory Index (DII)

A literature-derived scoring system developed by researchers at the University of South Carolina that quantifies how pro- or anti-inflammatory a person's overall diet is, on a scale from about -8.87 (most anti-inflammatory) to +7.98 (most pro-inflammatory). Anti-inflammatory inputs include magnesium, beta-carotene, omega-3s, fiber, and turmeric, while saturated fat, cholesterol, and trans fat push the score positive. Higher DII scores have been linked in observational studies to cardiovascular disease, certain cancers, and all-cause mortality.

Related: Mediterranean Diet, MIND Diet, Anti-Inflammatory Diet

Anti-Inflammatory Diet

An eating pattern emphasizing whole foods that reduce chronic low-grade inflammation, broadly modeled on the Mediterranean diet. Hallmarks include high intake of vegetables, fruits, fatty fish, olive oil, nuts, legumes, and spices like turmeric and ginger, with minimal refined grains, added sugars, and processed meats. Andrew Weil's popular version adds specific serving targets, but the broader concept is supported by reductions in CRP and IL-6 seen in multiple intervention trials.

Related: Dietary Inflammatory Index (DII), Mediterranean Diet, MIND Diet

Paleo Diet

An eating pattern that aims to mimic the presumed diet of Paleolithic hunter-gatherers, excluding grains, legumes, dairy, refined sugar, and processed foods. Short-term trials show improvements in weight, blood pressure, and glucose tolerance, though these are largely attributable to the elimination of ultra-processed foods rather than any unique mechanism. Critics note that modern paleo foods bear little resemblance to their ancient counterparts, and that legumes and whole grains have solid evidence behind them.

Related: Carnivore Diet, Mediterranean Diet, Ultra-Processed Foods (UPF)

Gluten-Free Diet

An eating pattern that eliminates gluten, a protein found in wheat, barley, rye, and their derivatives. It is medically necessary for people with celiac disease, which affects about 1% of the population, and for those with non-celiac gluten sensitivity. For everyone else, going gluten-free offers no clear health benefit and can lead to lower intakes of fiber, B vitamins, and whole grains if not carefully planned.

Osteopenia

A condition in which bone mineral density is lower than normal but not low enough to meet the threshold for osteoporosis, defined by a T-score between -1.0 and -2.5 on a DEXA scan. It is extremely common, affecting roughly half of adults over 50. Weight-bearing exercise, adequate calcium, vitamin D, and protein, plus avoidance of smoking and excessive alcohol, can slow progression to osteoporosis.

Related: Osteoporosis, Sarcopenia

Osteoporosis

A skeletal disorder characterized by low bone mass and deterioration of bone tissue, defined by a DEXA T-score of -2.5 or lower. Roughly one in three women and one in five men over 50 will experience an osteoporotic fracture, with hip fractures carrying a one-year mortality rate around 20%. Treatment combines resistance training, calcium and vitamin D, and for high-risk patients, medications such as bisphosphonates or denosumab.

Related: Osteopenia, Sarcopenia

Prediabetes

A metabolic state in which blood glucose is above normal but below the diabetes threshold, defined by fasting glucose of 100 to 125 mg/dL, an A1C of 5.7 to 6.4%, or a 2-hour oral glucose tolerance test of 140 to 199 mg/dL. About 96 million American adults have prediabetes, and more than 80% of them are unaware. The Diabetes Prevention Program showed that 5 to 7% weight loss plus 150 minutes of weekly activity reduces progression to type 2 diabetes by 58%.

Related: A1C (Hemoglobin A1C), Insulin Resistance, Metabolic Syndrome

Gestational Diabetes

Glucose intolerance that is first recognized during pregnancy, affecting 6 to 9% of pregnancies in the United States and typically screened for between 24 and 28 weeks. Risk factors include advanced maternal age, overweight, family history of diabetes, and certain ethnicities. Treatment focuses on dietary modification, glucose monitoring, and exercise, with insulin or metformin added if targets are not met, since untreated GDM raises risks of preeclampsia, cesarean delivery, and future type 2 diabetes.

Related: Prediabetes, Insulin Resistance

Eosinophilic Esophagitis (EoE)

A chronic allergic inflammatory disease of the esophagus in which eosinophils accumulate in the tissue, causing difficulty swallowing, food impaction, and reflux-like symptoms that do not respond to acid blockers. Prevalence has risen sharply over the past two decades, especially in developed countries, and it is now a leading cause of food getting stuck in the esophagus in adults. The six-food elimination diet, removing milk, wheat, egg, soy, nuts, and seafood, induces remission in many patients.

Related: FODMAP, Gluten-Free Diet

Anemia

A condition in which the blood has fewer red blood cells or less hemoglobin than normal, reducing oxygen delivery to tissues. Iron deficiency is the most common cause worldwide, but anemia can also result from inadequate B12 or folate, chronic disease, blood loss, or inherited disorders like sickle cell trait. The WHO defines anemia in non-pregnant adults as hemoglobin below 13 g/dL in men and 12 g/dL in women.

Related: Bioavailability, Tannins, Phytates (Phytic Acid)

Hypertension

Persistently elevated blood pressure, defined by the American College of Cardiology and American Heart Association as 130/80 mmHg or higher. It affects nearly half of U.S. adults and is the leading modifiable risk factor for stroke, heart attack, and kidney disease. The DASH diet, sodium reduction to under 2,300 mg per day, regular aerobic exercise, and weight loss can each lower blood pressure by 5 to 10 mmHg.

Related: DASH Diet, ASCVD, Pulse Pressure

Sarcopenic Obesity

The combination of low skeletal muscle mass and excess body fat, often seen in older adults who appear normal weight or only mildly overweight on a BMI scale. The condition is doubly harmful because the missing muscle reduces metabolic health and physical function while the excess fat worsens insulin resistance and inflammation. Resistance training and adequate protein, 1.2 to 1.6 g/kg per day spread across meals, are the cornerstones of treatment.

Related: Sarcopenia, Body Mass Index (BMI), FFMI (Fat-Free Mass Index)

Beta-Alanine

A non-essential amino acid that combines with histidine to form carnosine, a muscle buffer that slows pH drop during high-intensity exercise. Supplementation of 4 to 6 grams per day for 4 to 8 weeks reliably raises muscle carnosine by 40 to 60%, improving performance in efforts lasting 1 to 4 minutes. A harmless tingling sensation called paresthesia is the most common side effect, which can be avoided with divided doses or sustained-release formulations.

Related: Creatine Monohydrate, Caffeine

L-Citrulline

An amino acid that the kidneys convert to L-arginine, which in turn drives nitric oxide production and vasodilation. Supplementing 6 to 8 grams of citrulline, or 3 to 5 grams of citrulline malate, about an hour before exercise can improve blood flow, reduce muscle soreness, and modestly boost endurance. Citrulline raises plasma arginine more effectively than arginine itself because it bypasses liver metabolism.

Related: Creatine Monohydrate, Beta-Alanine

Adaptogens

A loosely defined category of herbs and mushrooms purported to help the body respond to stress by modulating cortisol and the HPA axis. Common examples include ashwagandha, rhodiola, holy basil, panax ginseng, and reishi mushroom. Evidence is mixed: ashwagandha has the strongest trial data for stress and sleep, while most others have small, short studies or rely on traditional use rather than rigorous trials.

Related: Nootropics

Nootropics

Substances taken to enhance cognitive function, including memory, focus, and motivation. Caffeine and L-theanine are the best-supported pair, with reliable improvements in attention and alertness, while racetams, modafinil, and complex stacks have weaker or prescription-only evidence. Most over-the-counter nootropics have small or no measurable effects in healthy adults, and long-term safety data are limited.

Related: Caffeine, Adaptogens

Magnesium

An essential mineral involved in more than 300 enzymatic reactions, including ATP metabolism, muscle contraction, nerve function, and DNA synthesis. The NIH recommends 400 to 420 mg per day for adult men and 310 to 320 mg for women, but national surveys show roughly half of U.S. adults fall short. Forms like glycinate, malate, and citrate are better absorbed than oxide, which is common in cheap supplements but poorly bioavailable and more likely to cause diarrhea.

Related: Bioavailability, Electrolytes

Waist-to-Height Ratio

A simple anthropometric index calculated by dividing waist circumference by height, with both measured in the same units. A ratio below 0.5 is generally recommended, with values above 0.5 indicating elevated cardiometabolic risk regardless of BMI. Multiple systematic reviews have found it predicts cardiovascular disease and diabetes at least as well as, and often better than, BMI or waist circumference alone.

Related: Body Mass Index (BMI), Visceral Fat

Body Adiposity Index (BAI)

A body fat estimation method that uses hip circumference and height, with no need for a scale. Proposed in 2011 as an alternative to BMI, the formula is hip circumference divided by height raised to the 1.5 power, then minus 18 to yield an approximate percentage body fat. Subsequent validation studies have been mixed, with BAI tending to overestimate body fat in lean individuals and underestimate it in those with obesity.

Related: Body Mass Index (BMI), FFMI (Fat-Free Mass Index)

Resting Heart Rate

The number of heartbeats per minute when a person is awake, seated or lying, and has not recently eaten, exercised, or been stressed. The normal adult range is 60 to 100 bpm, but well-trained endurance athletes often sit in the 40s or 50s because each stroke volume is larger. A resting heart rate that trends upward over time can signal overtraining, dehydration, illness, or developing cardiovascular disease.

Related: Heart Rate Variability (HRV), VO2 Max

Heart Rate Variability (HRV)

The beat-to-beat variation in the time interval between heartbeats, measured in milliseconds and reflecting the balance of sympathetic and parasympathetic nervous activity. Higher HRV generally indicates better cardiovascular fitness and recovery, while sustained low HRV is associated with stress, illness, overtraining, and increased mortality. Most consumer wearables report rMSSD or SDNN, the two most common time-domain metrics, and track day-to-day trends rather than absolute values.

Related: Resting Heart Rate, VO2 Max

Appendicular Skeletal Muscle Mass (ASMM)

The total mass of skeletal muscle in the arms and legs, typically measured by DEXA and used as a proxy for whole-body skeletal muscle. The Foundation for the National Institutes of Health sarcopenia project defines low muscle mass in older adults as ASMM adjusted for BMI below 0.789 in men and 0.512 in women. It is the most widely used muscle endpoint in clinical sarcopenia research.

Related: FFMI (Fat-Free Mass Index), Sarcopenia

Postbiotics

Beneficial compounds produced when gut bacteria ferment prebiotic fibers, including short-chain fatty acids, peptides, vitamins, and bacterial cell fragments. The International Scientific Association for Probiotics and Prebiotics defined the term in 2021 to encompass preparations of inanimate microorganisms or their components that confer a health benefit. Postbiotics are increasingly attractive to researchers because they avoid the stability and safety issues of live probiotics.

Related: Prebiotics, Probiotics, Short-Chain Fatty Acids (SCFAs)

Gut Microbiome

The trillions of bacteria, archaea, viruses, and fungi that live in the gastrointestinal tract, with the largest concentration in the colon. A typical adult gut microbiome contains 500 to 1,000 species and weighs an estimated 200 grams, with diversity generally associated with better metabolic and immune health. Diet is the strongest modifiable driver, with fiber-rich plant foods, fermented foods, and a wide variety of plants all increasing diversity within days.

Related: Prebiotics, Probiotics, Postbiotics

Short-Chain Fatty Acids (SCFAs)

The main metabolic products of colonic bacterial fermentation of dietary fiber, with acetate, propionate, and butyrate making up about 90% of the total. Butyrate is the primary fuel for colonocytes, propionate is largely used by the liver for gluconeogenesis, and acetate circulates systemically. Beyond energy, SCFAs regulate gut barrier integrity, immune function, and appetite, which is part of why high-fiber diets are linked to lower rates of colorectal cancer and metabolic disease.

Related: Soluble Fiber, Prebiotics, Postbiotics

Maillard Reaction

A non-enzymatic browning reaction between reducing sugars and amino acids that occurs when foods are cooked at temperatures above about 285 degrees F (140 degrees C) with low moisture. It is responsible for the brown crust on bread, the sear on a steak, the roast on coffee beans, and the toast on marshmallows. Hundreds of flavor and aroma compounds are generated, but so is acrylamide, a probable human carcinogen formed in starchy foods like fries and potato chips.

Related: Caramelization, Fermentation

Caramelization

The pyrolysis of sugar that occurs when sugars are heated to around 340 degrees F (170 degrees C) or higher, producing the characteristic brown color and complex flavor of caramel. Unlike the Maillard reaction, it does not require amino acids, only sugars, and it generates a different set of flavor compounds including diacetyl, furans, and esters. The reaction is fundamental to making caramel sauce, flan, creme brulee, and many dark-roast beers.

Related: Maillard Reaction

Emulsification

The process of combining two immiscible liquids, typically oil and water, into a stable mixture called an emulsion. Mayonnaise, vinaigrette, milk, butter, and ice cream all depend on emulsifiers, which are molecules with hydrophilic and lipophilic ends that coat droplets and prevent them from coalescing. Natural emulsifiers include lecithin from egg yolk and soy, while processed foods often use mono- and diglycerides, polysorbates, or carrageenan.

Related: Lecithin

Fermentation

A metabolic process in which microorganisms, such as bacteria, yeasts, or molds, convert sugars and starches into acids, gases, or alcohol. In food production, fermentation is used to make yogurt, kefir, sauerkraut, kimchi, kombucha, sourdough, cheese, miso, and tempeh, often improving digestibility, extending shelf life, and producing beneficial bioactive compounds. Properly fermented foods are also a dietary source of live cultures, though many commercial products are pasteurized after fermentation.

Related: Pasteurization, Probiotics, Postbiotics

Pasteurization

A heat treatment, named after Louis Pasteur, that kills pathogenic microorganisms and reduces spoilage bacteria in foods and beverages. Standard milk pasteurization, for example, heats to 161 degrees F (72 degrees C) for 15 seconds, which destroys Mycobacterium tuberculosis and Coxiella burnetii without significantly altering flavor or nutritional value. Raw milk advocates claim benefits from unpasteurized dairy, but the CDC and FDA report that raw milk is far more likely to cause foodborne illness than pasteurized milk.

Related: Fermentation