Glossary: Nutrition Terms
The nutrition vocabulary used in fitness, defined without the marketing.
Last updated: 1 July 2026
Overview
Nutrition has more jargon per square inch than almost any other part of fitness, and a good deal of it exists to sell things. These are the terms worth knowing.
Quick Answer
Key nutrition terms include macros, the three energy-providing nutrients; TDEE, your total daily energy expenditure; BMR, the energy used at complete rest; and calorie deficit, eating less than you expend.
Energy and expenditure
| Term | Definition |
|---|---|
| Calorie | A unit of energy. Food labels use kilocalories |
| BMR | Basal metabolic rate, energy used at complete rest |
| TDEE | Total daily energy expenditure, your maintenance |
| NEAT | Non-exercise activity thermogenesis, energy from daily movement |
| TEF | Thermic effect of food, energy used digesting it |
| Energy balance | Intake compared with expenditure |
| Calorie deficit | Eating less than you expend |
| Calorie surplus | Eating more than you expend |
| Maintenance | Intake at which bodyweight is stable |
Macronutrients
| Term | Definition |
|---|---|
| Macronutrient | Protein, carbohydrate or fat |
| Micronutrient | Vitamins and minerals |
| Protein | 4 calories per gram, supplies amino acids |
| Carbohydrate | 4 calories per gram, main fuel for hard exercise |
| Fat | 9 calories per gram, essential for hormones |
| Fibre | Indigestible carbohydrate, aids satiety and digestion |
| Amino acid | The building blocks of protein |
| Essential amino acid | One the body cannot make, must come from food |
| Leucine | The amino acid most linked to triggering muscle building |
| Complete protein | Contains all essential amino acids in useful amounts |
Dieting terms
| Term | Definition |
|---|---|
| Cut | A phase of deliberate fat loss |
| Bulk | A phase of deliberate weight and muscle gain |
| Lean bulk | Gaining slowly in a small surplus |
| Recomposition | Gaining muscle and losing fat simultaneously |
| Refeed | A planned period at higher calories, usually carbohydrate |
| Diet break | A planned period at maintenance |
| Reverse dieting | Gradually raising calories after a deficit |
| Flexible dieting | Any food fits if it meets your targets |
| Satiety | How full and satisfied a food leaves you |
Food and metabolism
| Term | Definition |
|---|---|
| Glycogen | Stored carbohydrate in muscle and liver |
| Glycaemic index | How quickly a food raises blood glucose |
| Insulin | A hormone regulating nutrient storage |
| Ketosis | A metabolic state from very low carbohydrate intake |
| Whole food | Minimally processed, close to its natural state |
| Ultra-processed | Industrially formulated with additives |
| Bioavailability | How well a nutrient is absorbed and used |
| Nutrient density | Nutrients relative to calories |
Terms that mostly mean nothing
| Term | Reality |
|---|---|
| Detox | Your liver and kidneys already do this |
| Clean eating | No agreed definition, varies by whoever is speaking |
| Superfood | A marketing term with no scientific definition |
| Metabolic damage | Not a recognised condition. Adaptation is real, damage is not |
| Fat burning zone | Real but largely irrelevant to fat loss |
| Toxins | Rarely specified by those selling their removal |
Common Mistakes
| Confusion | Clarification |
|---|---|
| BMR is a calorie target | It is not. TDEE is your maintenance estimate |
| A calorie on a label is a calorie | It is a kilocalorie, and carries up to 20 percent tolerance |
| Net carbs are standardised | Definitions vary by country and manufacturer |
| Clean food cannot cause fat gain | Energy balance applies to all food |
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR is the energy you would use lying still all day. TDEE includes everything else: movement, exercise and digestion. TDEE is always higher.
What does NEAT stand for?
Non-exercise activity thermogenesis, the energy used in everyday movement like walking, fidgeting and standing. It varies enormously between people.
What is a refeed?
A planned short period of higher calorie intake, usually from carbohydrate, during a fat loss phase. It restores glycogen and can help psychologically.
Is clean eating a useful concept?
Not as usually used. Prioritising minimally processed, nutrient dense foods is sensible; the moral framing of foods as clean or dirty is not.
Sources
British Nutrition Foundation - https://www.nutrition.org.uk/
British Dietetic Association food facts - https://www.bda.uk.com/food-health/food-facts.html