Slimming & Nutrition Glossary: Key Dieting Terms Demystified

B

BMI (body mass index) — your weight in kilograms divided by your height in metres squared. A healthy range for most adults is 18.5–24.9. For adults of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, NICE uses lower thresholds (overweight from 23, obesity from 27.5). It's a useful screening tool but doesn't distinguish muscle from fat.

BMR (basal metabolic rate) — the energy your body uses at complete rest to keep you alive: breathing, circulation, maintaining temperature.

C

Calorie (kcal) — a unit of energy. On UK labels, 'calories' means kilocalories.

Calorie density (energy density) — the number of calories in a given weight of food. Low-density foods such as vegetables, fruit and soups let you eat more for fewer calories.

Calorie deficit — eating fewer calories than you use, which causes weight loss over time.

F

Fibre — the part of plant foods that isn't fully digested. It aids fullness and digestion. UK adults are advised to eat 30g a day.

Free sugars — sugars added to food or drink, plus those in honey, syrups, nectars, fruit and vegetable juices, smoothies and purées. Adults should have no more than 30g a day.

G

Glycaemic index (GI) — a ranking of how quickly carbohydrate foods raise blood sugar. Low-GI foods such as oats and pulses release energy slowly. GI alone doesn't tell you whether a food is healthy.

M

Macronutrients — protein, carbohydrate and fat, the nutrients that provide energy.

MET (metabolic equivalent) — a measure of how much energy an activity uses compared with sitting still. Used in our activity calculator.

Micronutrients — vitamins and minerals, needed in small amounts.

N

NEAT (non-exercise activity thermogenesis) — energy used in daily movement that isn't formal exercise, such as walking, standing and housework.

P

Plateau — a period when weight stays the same despite following your plan. Common and usually temporary.

R

Reference Intake (RI) — the guideline amounts of energy and nutrients shown on UK food labels, based on an average adult needing 2,000kcal a day.

S

Satiety — the feeling of fullness after eating. Protein, fibre and water-rich foods score highly.

Satiety index — a ranking of foods by how full they make people feel per calorie. Boiled potatoes famously scored highest in early research.

T

TDEE (total daily energy expenditure) — all the energy you use in a day: BMR plus digestion plus activity. Eating below your TDEE leads to weight loss.

Traffic-light labelling — the colour-coded front-of-pack labels showing whether a food is high (red), medium (amber) or low (green) in fat, saturated fat, sugars and salt.