Health Glossary

Adjusted Body Weight (AjBW)

A clinical calculation that adds a fraction (typically 40%) of the weight above ideal body weight to IBW, providing a more accurate dosing weight for obese patients.

Android (apple) fat distribution

A pattern where fat concentrates around the abdomen and trunk, more common in men and associated with higher cardiovascular and metabolic risk than peripheral fat storage.

Android fat distribution

A pattern of fat storage concentrated around the abdomen (apple shape), more common in men and associated with higher cardiovascular and metabolic risk than fat stored on the hips and thighs.

Avoirdupois pound (lb)

The standard pound used in the US and UK, defined since 1959 as exactly 0.45359237 kilograms.

BAPEN

British Association for Parenteral and Enteral Nutrition, the body that developed MUST.

Bariatric surgery

Surgical procedures (gastric sleeve, gastric bypass, gastric band) that modify the digestive system to produce substantial, durable weight loss. Generally recommended for BMI 40+ or BMI 35+ with comorbidities when conservative measures are insufficient.

Source: National Institute for Health and Care Excellence (NICE)

Bioelectrical Impedance Analysis (BIA)

A method used by body composition scales that passes a tiny electrical current through the body to estimate fat, muscle, and water percentages based on differences in electrical conductivity.

BMI (Body Mass Index)

A numerical value calculated by dividing weight in kilograms by height in metres squared. Used globally as a screening tool to categorise weight as underweight, normal, overweight, or obese.

Source: World Health Organization

BMI Categories

Underweight: <18.5; Normal: 18.5-24.9; Overweight: 25-29.9; Obese Class I: 30-34.9; Obese Class II: 35-39.9; Morbidly Obese (Class III): 40+.

Source: World Health Organization

BMI Percentile (Children)

For children and teens, BMI is plotted on age- and sex-specific growth charts. Below 5th percentile is underweight; 85th–94th is overweight; 95th+ is obese.

Source: CDC Growth Charts

BMI Prime

A ratio derived by dividing BMI by 25 (the upper limit of the healthy BMI range), used as a more intuitive scale for weight classification.

BMI Scale

The standardised classification system adopted by the World Health Organization that maps Body Mass Index values to weight status categories (underweight, normal, overweight, obese). Used globally for health screening and population health surveillance.

Source: World Health Organization

Body composition

The proportion of fat, muscle, bone, and water in the body. Two people at the same weight can have very different body compositions.

Body Frame Size

A measure of skeletal breadth, often estimated by the wrist test: fingers overlap = small frame, fingers touch = medium, fingers don't touch = large frame. Frame size shifts ideal weight by roughly ±10%.

Source: Elbow breadth method — Metropolitan Life Insurance Co.

Body Mass Index (BMI)

A numerical value calculated by dividing weight in kilograms by the square of height in metres. The NHS uses BMI to screen adults for underweight (<18.5), healthy weight (18.5–24.9), overweight (25–29.9), and obesity (30+).

Source: World Health Organization

Body Mass Index Chart

A reference table that displays pre-calculated BMI values for common height and weight combinations, allowing instant visual identification of weight category (underweight, normal, overweight, obese) without manual calculation.

Source: National Institutes of Health

Body recomposition

The process of simultaneously losing fat and gaining muscle, typically achieved through strength training and adequate protein intake while eating at or near maintenance calories.

Body weight percentage

A normalised measure of weight change relative to starting weight, used in medical settings and weight loss competitions to compare progress across different body sizes.

Central adiposity

Fat stored around the abdomen and internal organs; particularly elevated in South Asian populations and strongly linked to insulin resistance.

Central Obesity

Excess fat stored around the abdomen, measured by waist circumference (>35 in for women, >40 in for men). A stronger predictor of cardiovascular risk than BMI alone.

Clinically significant weight loss

A weight reduction of 5% or more of initial body weight, recognised by WHO, NHS, and ADA as the minimum threshold for measurable health improvement in blood pressure, blood sugar, and cholesterol.

Devine Formula

The most widely referenced IBW formula: Men = 50 kg + 2.3 kg per inch over 5 ft; Women = 45.5 kg + 2.3 kg per inch over 5 ft.

Source: Devine BJ, 1974

DEXA scan

Dual-Energy X-ray Absorptiometry — a gold-standard body composition scan accurate to within 1–2% body fat.

Edmonton Obesity Staging System

A clinical framework that classifies obesity from Stage 0 to Stage 4 based on actual health impairments rather than weight alone.

Ethnic BMI adjustment

Lower BMI thresholds recommended by the NHS for South Asian, Chinese, and African-Caribbean populations, where overweight starts at BMI 23 and obesity at 27.5 instead of the standard 25 and 30.

Ethnicity-adjusted BMI

Lower BMI cut-offs (23 / 27.5) used for South Asian, Chinese, Black, and Middle Eastern adults to better reflect their cardiometabolic risk.

Fat-Free Mass Index (FFMI)

A body composition metric calculated as fat-free mass in kg divided by height in metres squared. Useful for assessing muscular development independently of fat mass.

Foot (ft)

An imperial unit of length equal to exactly 30.48 centimetres or 12 inches. Used for height measurement primarily in the US and UK.

Frankfort plane

The standard head position for height measurement where the lower edge of the eye socket and the upper margin of the ear canal are in a horizontal line.

GMI (Glucose Management Indicator)

A metric that estimates average blood sugar (HbA1c equivalent) from continuous glucose monitor data using the formula: GMI (%) = 3.31 + (0.02392 × mean glucose in mg/dL).

Gynoid (pear) fat distribution

A pattern where fat is stored primarily in the hips, thighs, and buttocks, more common in women and generally associated with lower metabolic risk than abdominal fat.

Gynoid Fat Distribution

A pattern where body fat is concentrated on the hips, buttocks, and thighs (pear shape). More common in pre-menopausal women and associated with lower metabolic risk than android distribution.

Healthy BMI Range

A BMI between 18.5 and 24.9, considered the window of lowest risk for weight-related health conditions in most adult populations.

Source: World Health Organization

Ideal Body Weight (IBW)

A clinical estimate of the weight associated with the lowest health risk for a given height, derived from formulas developed by researchers including Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964).

Source: Devine BJ, 1974

Imperial BMI formula

(weight in pounds ÷ height in inches squared) × 703 — gives the same result as the metric formula.

Insulin resistance

A condition where muscle and liver cells respond poorly to insulin, meaning glucose stays in the bloodstream instead of being absorbed. It is the primary mechanism linking excess visceral fat to type 2 diabetes.

Kilogram (kg)

The base unit of mass in the International System of Units (SI), used in most countries worldwide for measuring body weight.

Load cell

A precision force sensor used in digital scales that converts the mechanical force of body weight into an electrical signal for accurate measurement.

Mass

The quantity of matter in an object, measured in kilograms (kg). It is an intrinsic property that does not change with location or gravity.

MET (Metabolic Equivalent of Task)

A measure of exercise intensity where 1 MET equals resting energy expenditure. Brisk walking is 5.0 METs, meaning it burns 5× the calories of sitting still.

Metabolically Healthy Obesity (MHO)

A condition where an individual has a BMI ≥30 but maintains normal blood pressure, blood sugar, cholesterol, and inflammatory markers. Affects 10–30% of obese individuals, though research shows over half transition to metabolically unhealthy within 10 years.

Source: Journal of the American College of Cardiology

Morbid Obesity

A BMI of 40 or above, also called Class III obesity, where excess body fat significantly increases the risk of life-threatening health conditions.

Source: World Health Organization

MUST score

Malnutrition Universal Screening Tool — a 5-step screen that classifies adults as low, medium, or high risk of malnutrition.

NEAT (Non-Exercise Activity Thermogenesis)

The energy burned through all daily movement that isn't intentional exercise — fidgeting, standing, walking to the kitchen, taking stairs. It can vary by 200–900 calories/day between sedentary and active individuals.

New BMI

A 2013 modification of BMI by Nick Trefethen using height to the power 2.5, formula: 1.3 × weight (kg) ÷ height (m)^2.5.

NHS BMI categories

The six-tier classification system used by the National Health Service to categorise adult weight status: underweight (<18.5), healthy weight (18.5–24.9), overweight (25–29.9), obese class I (30–34.9), obese class II (35–39.9), and severely obese class III (40+).

Source: NHS England

NHS BMI colour coding

The NHS uses a traffic-light system for BMI categories: green for healthy weight (18.5–24.9), amber for overweight (25–29.9), and red shades for obese classes (30+).

NICE guidelines

Clinical guidelines published by the National Institute for Health and Care Excellence that NHS practitioners follow for evidence-based treatment decisions, including obesity management (NICE CG189).

Source: NICE

NICE PH46

National Institute for Health and Care Excellence Public Health Guideline 46, which established lower BMI thresholds for ethnic minority populations in the UK in 2013.

Non-Scale Victory (NSV)

A positive health outcome from weight loss not captured by the scale — such as better sleep, looser clothing, improved blood work, or greater energy.

Normal-Weight Obesity

A condition where an individual has a BMI within the normal range (18.5–24.9) but carries an abnormally high percentage of body fat (>25% for men, >35% for women), often due to low muscle mass and sedentary lifestyle.

Source: European Heart Journal

Obesity

A chronic, complex disease defined by a BMI of 30.0 kg/m² or above, characterised by excessive body fat accumulation that impairs health. Classified into three tiers of increasing severity by the WHO.

Source: World Health Organization

Obesity paradox

The epidemiological finding that moderate overweight (BMI 25–29.9) is associated with lower mortality in older adults compared to normal weight, possibly due to nutritional reserves during illness.

Overweight (BMI 25–29.9)

A WHO BMI category indicating weight above the normal range. Associated with modestly increased risks for type 2 diabetes, hypertension, and cardiovascular disease.

Personal BMI Target

An individualised healthy BMI range that accounts for a person's age, gender, ethnicity, fitness level, and body frame size, rather than applying the universal 18.5–24.9 threshold to all adults equally.

Quetelet Index

The original name for what is now called BMI, developed by Belgian mathematician Adolphe Quetelet in the 1830s for population-level body size analysis.

Source: Keys A. Journal of Chronic Diseases. 1972

Sarcopenia

The progressive loss of skeletal muscle mass and strength that occurs with ageing, accelerating after age 50. Resistance training is the primary evidence-based intervention to slow or reverse it.

Source: Age and Ageing, Oxford Academic

Sarcopenic obesity

A state of low muscle mass and high fat mass, common in older adults; not detected by BMI alone.

Skin-fold Callipers

A device that measures the thickness of pinched skin and fat at specific body sites to estimate body fat percentage using formulas like Jackson-Pollock.

Skinfold caliper

A device that measures the thickness of subcutaneous fat folds at specific body sites to estimate total body fat percentage.

Somatotype

A classification system of human physiques into ectomorph, mesomorph, and endomorph categories, originally developed by psychologist William Sheldon in the 1940s.

Speakable Specification

A schema.org property that identifies sections of a web page most suitable for audio playback and voice assistant responses, helping AI assistants extract and cite the most relevant content.

Stone (st)

A unit of weight equal to 14 pounds (6.35 kg), still commonly used in the UK and Ireland for expressing body weight.

TDEE (Total Daily Energy Expenditure)

The total number of calories your body burns in a day including basal metabolism, physical activity, and the thermic effect of food. Weight loss requires eating below your TDEE.

Thermic effect of food (TEF)

The energy cost of digesting and processing food. Protein has the highest TEF at 20–30%, carbs 5–10%, and fat 0–3%, which is why high-protein diets burn more calories at rest.

Visceral Fat

Fat stored deep within the abdominal cavity surrounding vital organs. Metabolically active and strongly linked to cardiovascular disease, type 2 diabetes, and chronic inflammation. Measured indirectly via waist circumference.

Source: NHS

Waist Circumference

A measurement taken at the navel level used to assess visceral fat. Risk thresholds: >31.5 in / 80 cm (women) or >37 in / 94 cm (men) for increased risk.

Waist-to-height ratio

Waist circumference divided by height. A ratio under 0.5 is healthy; over 0.55 indicates increased cardiometabolic risk.

Waist-to-hip ratio (WHR)

A measurement calculated by dividing waist circumference by hip circumference. A WHR above 0.90 for men or 0.85 for women indicates central obesity and elevated cardiovascular risk.

Weight

The force exerted on an object by gravity, calculated as mass × gravitational acceleration. Measured in newtons (N) in the SI system.

Weight Loss Percentage

A normalized metric calculated as [(Starting Weight - Current Weight) / Starting Weight] x 100, allowing comparison regardless of starting size.