Nutrition Basics
Plain-language explanations of the terms behind the calculators and the recipes — calories, macros, and how daily targets are figured. Each entry cites its sources.
Calorie
A calorie is a unit of energy — how much energy a food gives you, or how much your body uses.
Everything your body does, from sleeping to walking, runs on energy measured in calories. Eat about as many as you use and your weight holds steady; eat more and the extra is stored, eat fewer and your body draws on its reserves.
- On U.S. food labels, “Calories” means kilocalories (kcal).
- Food labels use a 2,000-calorie day as their reference.
Sources: FDA Daily Values (Nutrition Facts label), Dietary Guidelines for Americans (USDA & HHS)
Macronutrients
The three nutrients that give you calories: protein, carbohydrate, and fat.
“Macros” are the parts of food your body needs in large amounts and burns for energy. Each gram carries a set number of calories, so the mix of macros in a meal decides both its calorie total and how it helps your body.
- Protein: 4 calories per gram.
- Carbohydrate: 4 calories per gram.
- Fat: 9 calories per gram (the most calorie-dense).
Sources: Acceptable Macronutrient Distribution Ranges (National Academies), Dietary Guidelines for Americans (USDA & HHS)
Protein
A macronutrient that builds and repairs muscle and tissue, and helps you feel full.
Protein comes from foods like meat, fish, eggs, dairy, beans, and tofu. Beyond building the body, it is the most filling macronutrient, which is why higher-protein meals often help with appetite.
- Baseline need (RDA): about 0.8 g per kg of body weight.
- Active people often aim higher, roughly 1.2–2.2 g per kg.
- Recommended range: 10–35% of daily calories.
Sources: Acceptable Macronutrient Distribution Ranges (National Academies), Dietary Guidelines for Americans (USDA & HHS)
Carbohydrates
Your body’s main and quickest source of energy.
Carbohydrates include sugars, starches, and fiber — found in grains, fruit, vegetables, and dairy. Most become glucose your body uses for fuel; fiber is the exception and passes through largely undigested.
- Recommended range: 45–65% of daily calories.
- Provides 4 calories per gram.
Sources: Acceptable Macronutrient Distribution Ranges (National Academies), Dietary Guidelines for Americans (USDA & HHS)
Fat
A macronutrient used for energy, hormones, and absorbing certain vitamins.
Dietary fat comes from oils, nuts, dairy, and meat. It is essential in the diet, but because it packs more than twice the calories of protein or carbs per gram, portions add up quickly.
- Recommended range: 20–35% of daily calories.
- Provides 9 calories per gram.
Sources: Acceptable Macronutrient Distribution Ranges (National Academies), Dietary Guidelines for Americans (USDA & HHS)
Fiber
A type of carbohydrate your body can’t fully digest — it aids digestion and fullness.
Fiber comes from plant foods like whole grains, beans, fruit, and vegetables. It slows digestion, helps you feel full, and supports gut and heart health, all with few or no usable calories.
- Daily Value on labels: 28 g (on a 2,000-calorie diet).
Sources: FDA Daily Values (Nutrition Facts label), Dietary Guidelines for Americans (USDA & HHS)
BMR — Basal Metabolic Rate
The calories your body burns at complete rest just to keep you alive.
Your BMR covers breathing, circulation, and cell repair — the background work of staying alive. It is usually the largest share of what you burn each day. This tool estimates it with the Mifflin–St Jeor equation using your sex, age, height, and weight.
- Typically the biggest part of your daily calorie burn.
Sources: Mifflin–St Jeor equation
TDEE — Total Daily Energy Expenditure
The total calories you burn in a day: your BMR plus movement and activity.
TDEE is your resting burn (BMR) multiplied by an activity factor. It is roughly the number of calories that would keep your weight where it is — the starting point for setting a goal.
- Estimated as BMR × an activity multiplier.
- Approximately your “maintenance” calories.
Sources: Mifflin–St Jeor equation, Dietary Guidelines for Americans (USDA & HHS)
Activity Level
A multiplier applied to your BMR to estimate how much daily movement adds to your burn.
Rather than track every step, calculators use a rough factor for how active you are. Pick the one that matches a typical week — it is an estimate, so when in doubt choose the lower option.
- Not very active: ×1.2
- Lightly active (1–3 days/week): ×1.375
- Moderately active (3–5 days/week): ×1.55
- Very active (6–7 days/week): ×1.725
- Extremely active (hard daily / physical job): ×1.9
Sources: Mifflin–St Jeor equation
Calorie Balance (Deficit & Surplus)
Eat fewer calories than you burn to lose weight, or more to gain — the difference is the balance.
A “deficit” means eating below your maintenance calories, which tends to lose weight over time; a “surplus” is above it, which tends to gain. These are estimates, and very low intakes can backfire — slower changes are usually easier to keep.
- About 3,500 calories ≈ 1 pound of body fat (a rule of thumb).
- So roughly 500 fewer calories a day ≈ about 1 pound a week.
Macro Ranges (AMDR)
Expert ranges for how much of your calories should come from each macronutrient.
The Acceptable Macronutrient Distribution Ranges, set by the National Academies, give healthy bands rather than single numbers — leaving room to shape a diet around your preferences and goals.
- Protein: 10–35% of calories.
- Carbohydrate: 45–65% of calories.
- Fat: 20–35% of calories.
Sources: Acceptable Macronutrient Distribution Ranges (National Academies)
Daily Value (%DV)
The reference amounts on the Nutrition Facts label, based on a 2,000-calorie diet.
The %DV shows how much one serving contributes toward a day’s worth of a nutrient. A quick rule: 5% or less is low, and 20% or more is high.
- Based on a 2,000-calorie reference diet.
- 5% DV or less = low; 20% DV or more = high.
Educational tool only — I am a home cook, not a registered dietitian or physician. These figures are general estimates, not medical or nutritional advice. Consult a qualified professional before changing your diet.