Full index

The NutritionDex A–Z

50 entries covering calorie-tracking concepts, energy balance, metabolic physiology, and the measurement and assessment vocabulary the modern quantified-self stack runs on. Each entry is editor-reviewed against primary sources.

Metabolic Physiology

• Adaptive Thermogenesis The specific reduction in energy expenditure beyond what fat-free-mass loss alone would predict, observed duri…
• BMR The minimum energy a body expends at complete rest to maintain vital functions — measured under strict fasting…
• Calorie Deficit A state in which caloric intake is lower than caloric expenditure over a sustained window — the driver of fat …
• Calorie Surplus A state in which caloric intake exceeds caloric expenditure — the driver of weight gain, whether that gain is …
• CICO The energy-balance framework stating that body-weight change over time equals caloric intake minus caloric exp…
• Energy Balance The relationship between caloric intake and caloric expenditure over a defined period — negative (deficit), ne…
• Energy Expenditure The total caloric cost of all physiological processes and activities over a given period — the "out" side of t…
• EPOC The elevated oxygen consumption — and associated caloric burn — in the hours following intense exercise, as th…
• Fat Oxidation The metabolic pathway by which stored or dietary fats are broken down and used to produce ATP — the primary fu…
• Glycemic Index A 0-100 scale ranking how rapidly and how high a carbohydrate-containing food raises blood glucose relative to…
• Glycemic Load The portion-corrected version of glycemic index: GL = GI × grams of available carbohydrate ÷ 100. A more pract…
• Glycogen Stores The body's stored carbohydrate reserve — 300-600 g held in muscle and liver as glycogen, rapidly mobilised for…
• Insulin Resistance A reduced responsiveness of cells to insulin, requiring the pancreas to produce more insulin to achieve the sa…
• Insulin Sensitivity The efficiency with which cells respond to insulin — higher sensitivity means less insulin needed to achieve a…
• Maintenance Calories The caloric intake at which body weight remains stable over time — equal to TDEE by definition, and the anchor…
• Metabolic Adaptation The umbrella term for the cluster of physiological changes that reduce total energy expenditure below predicte…
• Metabolic Flexibility The ability to efficiently switch between carbohydrate and fat as primary fuel sources in response to metaboli…
• NEAT Calories burned from all daily movement that is not deliberate exercise — walking, standing, fidgeting, chores…
• Recomposition The simultaneous reduction of fat mass and increase in lean mass at roughly maintenance calories — most achiev…
• Respiratory Quotient The ratio of CO2 produced to O2 consumed — a window into which fuel (fat, carb, protein) the body is primarily…
• RMR Energy expended at rest under non-strict conditions — typically 5-10% higher than true BMR and the value most …
• Set Point Theory The hypothesis that the body defends a genetically-biased body-weight range via coordinated adjustments in app…
• TDEE The total number of calories a person burns in a day — the sum of BMR, thermic effect of food, activity, and n…
• TEF The energy cost of digesting, absorbing, and storing food — roughly 10% of total intake on a mixed diet and su…
• Thermogenesis The production of heat in the body — the biophysical mechanism underlying BMR, TEF, NEAT, and exercise energy …
• VO2 Max The maximum rate at which a body can consume and utilise oxygen during exercise — the gold-standard metric for…

Dietary Assessment

• BIA A body-composition method that estimates fat-free mass by measuring the body's resistance to a low-level elect…
• Body Composition The proportional breakdown of body mass into fat mass, lean mass (muscle, bone, organs), and water — a more in…
• Body Fat Percentage Fat mass expressed as a percentage of total body mass — a headline metric for body composition, with accuracy …
• Bulking A deliberate, time-bounded caloric surplus intended to gain muscle mass — paired with progressive resistance t…
• Calipers (Skinfold) A spring-loaded device that measures the thickness of pinched subcutaneous fat at standardised body sites, use…
• Cutting A deliberate, time-bounded caloric deficit intended to reduce body fat while preserving lean mass — the fat-lo…
• DEXA A low-radiation X-ray scan that measures body composition with high accuracy — the clinical reference for fat …
• Diet Break A planned multi-day period (usually 7-14 days) at maintenance calories within a longer cut, intended to partia…
• Indirect Calorimetry The measurement of energy expenditure by quantifying oxygen consumption and carbon dioxide production — the st…
• Lean Body Mass Total body mass minus fat mass — everything non-fat: muscle, bone, organs, connective tissue, and body water.
• Net Carbs A tracking convention where fiber (and sometimes sugar alcohols) are subtracted from total carbohydrate to ref…
• Refeed A structured single-day or short-duration increase in caloric intake (typically from carbohydrates) during an …
• Reverse Dieting A structured, gradual increase in caloric intake following a cut, aimed at returning to maintenance without ra…
• Water Weight Body mass variation caused by hydration state and fluid retention rather than true tissue change — responsible…
• Weekly Average Weight The rolling 7-day mean of daily body-weight readings — the smoothed signal that reveals true body-composition …
• Weigh-In Variance The day-to-day fluctuation in body weight under consistent measurement conditions — typically 1-4 lbs, driven …

Macronutrient Science

• Carbohydrates The macronutrient composed of sugars, starches, and fibres — yielding 4 kcal per gram and the body's preferred…
• Fats The most energy-dense macronutrient at 9 kcal per gram — essential for hormone synthesis, membrane structure, …
• Fiber The non-digestible carbohydrate component of plant foods — effectively contributing 0-2 kcal per gram and supp…
• Macronutrients The three energy-yielding nutrients consumed in gram-scale quantities: protein, carbohydrate, and fat. Alcohol…
• Protein The macronutrient providing amino acids for tissue synthesis, enzyme production, and metabolic signalling — yi…

Biochemistry

• Ghrelin The "hunger hormone" secreted primarily by the stomach, rising before meals and after weight loss to drive app…
• Leptin The "satiety hormone" secreted by adipose tissue in proportion to fat mass, signalling long-term energy availa…
• Satiety The physiological signal that suppresses further food intake between meals — distinct from satiation, which en…