Energy
- Calorie
- A unit of energy. On food labels, a "calorie" is really a kilocalorie (kcal): the energy food gives your body.
- Metabolism
- All the chemical processes that keep you alive, including turning food into energy. "Fast" or "slow" metabolism varies less than people think.
- BMR
- Basal metabolic rate: the energy your body burns at complete rest just to stay alive. Usually the biggest part of daily burn.
- TDEE
- Total daily energy expenditure: all the calories you burn in a day. Eat about this much to keep your weight stable.
- Maintenance calories
- The number of calories that keeps your bodyweight stable — roughly equal to your TDEE.
- Calorie deficit
- Eating fewer calories than you burn. The body makes up the difference from stored energy, mostly fat — the basis of weight loss.
- Calorie surplus
- Eating more calories than you burn. The extra energy is stored — as muscle if you train for it, otherwise mostly as fat.
- NEAT
- Non-exercise activity thermogenesis: calories burned by everyday movement that isn't exercise — walking, fidgeting, chores.
- Thermic effect of food
- The energy your body uses to digest and process food — about 10% of calories eaten, and highest for protein.
Macronutrients
- Macronutrient
- One of the three nutrients we eat in large amounts and that provide calories: protein, carbohydrate, and fat. Often called macros.
- Protein
- A macronutrient made of amino acids, used to build and repair every tissue. From the nutrition side: where to get it and how much.
- Carbohydrate
- A macronutrient found in grains, fruit, vegetables, and sugar. The body's preferred fuel for the brain and hard exercise.
- Fat
- A macronutrient found in oils, nuts, meat, and dairy. The most energy-dense, and essential for hormones and absorbing some vitamins.
- Fiber
- The part of plant foods the body can't digest. It helps digestion, feeds gut bacteria, and keeps you full.
- Amino acid
- The building blocks of protein. The body links about 20 kinds together in different orders to make every protein it needs.
- Essential amino acids
- The nine amino acids the body can't make, so they must come from food. Leucine is key for building muscle.
- Glycemic index
- A 0–100 score for how quickly a carbohydrate food raises blood sugar, compared with pure glucose at 100.
Micronutrients & Hydration
- Micronutrient
- Vitamins and minerals: nutrients needed in tiny amounts, with no calories, but essential for the body to work.
- Vitamin
- An organic micronutrient the body needs in small amounts. Some dissolve in fat (A, D, E, K); others in water (B vitamins, C).
- Mineral
- An inorganic micronutrient from food, like calcium, iron, or potassium, needed for bones, blood, nerves, and more.
- Iron
- A mineral that helps red blood cells carry oxygen. Low iron is one of the world's most common deficiencies.
- Electrolyte
- Minerals that carry an electric charge in body fluids — sodium, potassium, magnesium, chloride — controlling nerves, muscles, and fluid balance.
- Hydration
- Having enough water in the body. Needs vary with size, heat, and activity; thirst and pale urine are practical guides.
- Sodium
- A mineral and electrolyte, mostly eaten as salt. Needed for nerves and fluid balance; most people eat more than recommended.
Body Composition
- Body fat percentage
- The share of your body weight that's fat. A better measure of body composition than weight alone.
- Lean mass
- Everything in your body except fat: muscle, bone, organs, and water. Often used loosely to mean muscle.
- BMI
- Body mass index: weight divided by height squared. A quick screening tool for populations, but a rough measure for individuals.
- Water weight
- Short-term changes in body weight caused by shifts in stored water, not fat. Salt, carbs, and hormones all move it.
- Bulking
- A phase of eating in a calorie surplus on purpose to support muscle growth. From the nutrition side: how big a surplus, and what to eat.
- Cutting
- A phase of eating in a calorie deficit on purpose to lose fat while keeping muscle. From the nutrition side: how fast, and what to eat.
- Body recomposition
- Losing fat and gaining muscle at the same time. From the nutrition side: eating around maintenance with plenty of protein.
Eating Patterns
- Meal timing
- When you eat across the day. It matters far less than what and how much you eat in total.
- Intermittent fasting
- An eating pattern that limits eating to certain hours or days, like 16:8. Works mainly by making it easier to eat less.
- Tracking macros
- Logging the grams of protein, carbs, and fat you eat, usually with an app, to hit set targets. Also called counting macros.
- Portion size
- How much of a food you actually eat at one time. Often different from the serving size on the label.
- Whole foods
- Foods that are unprocessed or minimally processed, close to their natural form: vegetables, fruit, eggs, meat, beans, whole grains.
- Diet
- Two meanings: everything you normally eat, and a planned eating pattern for a goal like weight loss.
- Cheat meal
- Gym slang for a planned meal that breaks your usual diet rules. Can help some people stick to a plan; can backfire for others.
- Ketosis
- A state where the body, short of carbohydrate, burns fat into ketones for fuel. The goal of the keto diet.
Supplements
- Supplement
- A product taken to add nutrients or compounds to your diet: vitamins, protein powder, creatine. Loosely regulated in many countries.
- Creatine
- A compound found in meat and fish that powers short, hard efforts. From the nutrition side: the most studied supplement, and what the evidence says on safety.
- Protein powder
- Protein extracted from milk, eggs, or plants and dried into a powder. A convenient way to add protein, not a magic muscle builder.
- Caffeine
- A stimulant in coffee, tea, and energy drinks. It improves alertness and exercise performance, but can hurt sleep.
- Pre-workout
- A supplement drink taken before training, usually built around caffeine plus other ingredients like beta-alanine.
- Multivitamin
- A supplement combining many vitamins and minerals in one pill. Can fill gaps in a limited diet, but doesn't replace good food.
- BCAA
- Branched-chain amino acids: three essential amino acids sold as a supplement. Largely unnecessary if you eat enough protein.
Reading Food
- Nutrition label
- The panel on packaged food listing calories, macros, and some micronutrients per serving or per 100 g.
- Serving size
- The standard amount a nutrition label's numbers refer to. Set by the manufacturer or regulations, not by how much you eat.
- Ultra-processed food
- Industrially made foods built mostly from refined ingredients and additives — soft drinks, packaged snacks, instant noodles.
- Calorie density
- How many calories a food contains per gram. Low-density foods let you eat more volume for fewer calories.
- Satiety
- The feeling of fullness and satisfaction after eating that keeps you from being hungry again soon.
- Added sugar
- Sugar added during processing or cooking, plus sugar in syrups and honey — not the sugar naturally in whole fruit or milk.