Nutrition glossary

Nutrition & Metabolism Glossary

No jargon, no fluff. Clear definitions of the metabolism and nutrition terms you'll run into while tracking — written so they actually make sense.

Each entry explains what the term means, why it matters for your goals, and how it shows up in WhispCal.

By Thomas MoriceBuilds WhispCal, and writes everything hereUpdated September 19, 2026

All terms

What Is TDEE?TDEE (Total Daily Energy Expenditure) is the total number of calories you burn in a day. It combines your resting metabolism, the energy used to digest food, everyday movement, and exercise.

What Is BMR?BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to stay alive — breathing, circulating blood, and running your organs. It makes up roughly 60–70% of your total daily energy expenditure.

What Are Macros?Macros (macronutrients) are the three nutrients that supply energy: protein and carbohydrates at 4 calories per gram, and fat at 9. While calories decide weight change, your macro split shapes whether that change is muscle or fat.

What Is Adaptive Thermogenesis?Adaptive thermogenesis is when your body burns fewer calories than predicted during a prolonged calorie deficit. As you diet, your metabolism downshifts beyond what weight loss alone explains, defending your body against further loss.

What Is Metabolic Adaptation?Metabolic adaptation is the body's response to prolonged dieting, where it burns fewer calories than predicted to defend against weight loss. It includes a lower resting metabolism, reduced everyday movement, and a smaller energy cost of activity.

What Is Reverse Dieting?Reverse dieting is the practice of gradually increasing your calories after a diet — usually a small weekly bump — to rebuild your metabolic rate while minimising fat regain. It's the bridge between a cut and a return to maintenance.

What Are Maintenance Calories?Maintenance calories are the number of calories you eat to keep your weight stable — the point where intake matches your total daily energy expenditure. Eat below it to lose, above it to gain.

What Is a Calorie Range?A calorie range is a flexible daily band of calories to aim for instead of one rigid number. It reflects how real eating and real metabolism vary day to day, giving you room to live while staying on track for your goal.

What Is NEAT?NEAT (Non-Exercise Activity Thermogenesis) is the energy you burn through all daily movement that isn't deliberate exercise — walking, fidgeting, standing, and chores. It varies enormously between people and can swing your daily burn by hundreds of calories.

What Is TEF?TEF (Thermic Effect of Food) is the energy your body spends digesting and processing what you eat. It accounts for roughly 10% of your daily calorie intake, and protein has by far the highest thermic effect of the macros.

How these terms fit together

Almost everything here hangs off one sum. Your TDEE is the total you burn in a day, and it is made of four parts that are nowhere near equal in size.

BMR — what you burn at complete rest, roughly 60 to 70% of the total and the largest piece by far
TEF — the energy spent digesting what you eat, about 10% of your intake
NEAT — walking, fidgeting, standing, chores, and the part that quietly drops when you diet
Exercise — deliberate training, and usually the smallest of the four
Maintenance calories — the name for eating at your TDEE, where weight holds steady

The terms that actually change what you do

Most definitions are trivia. Three of these change a decision.

Adaptive thermogenesis and metabolic adaptation describe why a deficit shrinks while you are sitting in it, which is the reason a target set once stops working. Reverse dieting is the way back up out of one without the fat returning. A calorie range is what to use instead of a single number when a single number makes you quit.

Why definitions matter here

Calorie tracking has a vocabulary problem. Apps use TDEE, maintenance and goal calories to mean overlapping things, and a formula's estimate and a measured figure get the same label even though one is a guess and the other is evidence.

Every entry says what the term means, why it matters for your goal, and how it shows up in WhispCal. Where an app would show you a number, these say where the number came from.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is what you would burn lying in bed all day. TDEE is that plus digestion, daily movement and exercise. TDEE is always the larger number, and it is the one a calorie target is built from.

What is a good TDEE to aim for?

TDEE is not a target, it is a measurement. You do not aim for one, you find yours and then decide how far above or below it to eat. Aiming for someone else's number is how people end up eating for a body they do not have.

Is metabolic adaptation permanent?

No. Most of it reverses when you eat at maintenance again, which is what a reverse diet is for. It is a response to a deficit, not damage from one.

Do I need to know any of this to track calories?

No. You can log meals and weigh in without a single definition. It starts to matter the moment progress stalls, because that is when the difference between an estimated burn and a measured one decides what you should do next.

Let WhispCal do the math automatically

These numbers are a starting point. WhispCal measures how your body actually responds — logging food in 3 seconds by voice, photo, or barcode — and auto-adjusts your targets as your metabolism changes. Free on iOS and Android.

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