What TDEE actually means (and what Mifflin-St Jeor is doing)

BMR, RMR, TEF, NEAT, and exercise

Basal metabolic rate (BMR) is energy at complete rest under strict lab conditions. Resting metabolic rate (RMR) is a related clinic measurement, slightly less strict. People mix the words. Mifflin-St Jeor was published as a predictive equation for resting energy expenditure (PubMed 2305711). Cook EZ uses that resting piece as the core of the calculator, then multiplies by activity.

Thermic effect of food (TEF) is the cost of digesting. It is often folded into the day's total rather than calculated bite by bite. NEAT is non-exercise activity: walking the kitchen, standing, fidgeting. Exercise is the planned session. Watches try to count some of this and often invent a lot of it. If you already picked a high activity factor, do not also add 600 kcal of "workout calories" from a wristband. That is double counting.

TDEE is the sum you are trying to approximate. Intake versus TDEE, over weeks, moves tissue. One day of a wedding does not.

A fever, a very hot kitchen shift, or a week of hiking will move expenditure. The calculator will not know unless you change the factor. Use the diary and the clothes. Then edit the sticky note on the fridge.

What Mifflin-St Jeor actually is

Mifflin and colleagues (1990) fitted equations from measured resting energy in a sample of adults. The common form is: 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5 for men, and the same with −161 instead of +5 for women. It is a linear fit. It is not your thyroid. It is not your amputation. It is not your extra 20 kg of muscle versus 20 kg of fat at the same scale weight (muscle is costlier, but the equation only sees weight).

Other equations exist (Harris-Benedict, Owen, Katch-McArdle if you have a body-fat estimate). Different apps pick different ones, then different activity tables. That is one reason two calorie calculators disagree before you even log food. Cook EZ documents Mifflin-St Jeor because it is widely used and the paper is citable.

Sex in the equation is the binary the paper used. If that does not describe you, work with a clinician on a starting budget. Do not let a form field become a medical event.

Height in the Mifflin equation is in centimeters. A 5-foot-4 person is about 163 cm. Typing 5.4 into a centimeter field will explode the number. Check the unit.

Body weight in the Mifflin piece should be current weight, in kilograms. Pounds divided by 2.2. People type pounds into a kilogram field and get a science-fiction TDEE. Check once. Then cook dinner at a human number.

Activity factors are the sloppy part

Sedentary, lightly active, moderately active, very active: these words hide a lot. A desk job plus a 30-minute walk is not "very active." A line cook on their feet for eight hours might be. If the calculator output feels like a banquet and you are gaining, the factor is too high or the log is missing oil. Lower the factor one step. Wait three weeks.

Training blocks change TDEE. So does a new baby (less sleep, more standing). Recalculate when weight has moved by a meaningful amount, because the Mifflin piece uses current weight. A 15 kg loss changes the resting estimate. People forget to update.

The Dietary Guidelines discuss calorie needs in ranges by age and activity in a different framework (Estimated Energy Requirement). You can read both. They will not match to the kcal. That is expected. Patterns still matter: vegetables, protein foods, grains. TDEE is the energy envelope, not the menu.

NEAT drops when you sit more after a job change. People call this "broken metabolism." Often it is a thousand fewer steps and a higher activity factor they never lowered.

Using the budget in a kitchen

A maintenance target is TDEE. A fat-loss target is a modest deficit (often 300 to 500 kcal if appropriate). A surplus is the reverse. Guardrails: very low intakes are a safety problem. Cook EZ will not cheer 900 kcal for an adult as a lifestyle.

Cook toward the budget. If protein is also a goal, use the macro calculator to split the calories, then generate dinners that put tofu, fish, legumes, or poultry on the board. FoodData Central tells you cooked yields. The diary tells you if you hit the split.

Leftovers and weekends: TDEE is a daily average idea. Weekly energy balance is what the scale sees. Logging Friday's pizza on Friday is better than fasting Monday to "make up for it" in a way you will rebound. FSIS still wants the leftover pizza reheated properly if it sat. Safety and energy are different jobs.

Protein targets sit inside the energy budget. 112 g of protein is about 448 kcal. The rest of TDEE is carbohydrate and fat. The macro calculator is just that split. Cook food that fills it.

A surplus for muscle gain still needs protein and a training stimulus. The calorie calculator will happily suggest more rice. The gym is not in the JSON. Put the protein on the plate using FoodData Central cooked yields.

When the number fails you

Edema, menstrual cycle water, creatine, a new resistance program (glycogen), and a salty restaurant weekend all move the scale without matching the diary. Use 2 to 4 week averages. Clothes. Measurements if you like them. Not Tuesday morning after sushi.

Medications, thyroid disease, and some conditions change expenditure. Equations will be wrong. That is a clinician lane. The app can still log food.

Adaptive thermogenesis: as you lose weight, TDEE drops more than some people expect (smaller body, possible NEAT drop). Recalculate. Do not copy a 2019 target forever.

If the scale and the diary disagree, oil and weekend portions are the first audit. Then the activity factor. Then three more weeks. Then a clinician if needed. The 1990 paper cannot see your thyroid.

The diary has to be in the same universe

A perfect TDEE estimate plus a diary that skips oil is a broken loop. Barcode, weigh dense foods, log recipe servings. See the companion pieces on portions and why apps disagree.

Plate photos are for mixed meals. They are worse than a scale and better than a hole in the day.

If you cook from Cook EZ, the card's nutrition is FDC-style math. Servings eaten is the cleanest path from TDEE budget to a real pot.

Keep cooking. A TDEE number that stops you from making dal is a bad use of an equation. Use it to pick a serving of rice, not to skip dinner.

If you hate tracking, use TDEE for a week to learn what a 600 kcal dinner looks like, then stop logging every herb. Keep logging oil and the dense foods. The equation was a teacher. The skillet is the job.

A worked example (not your body)

Suppose Mifflin-St Jeor gives 1500 kcal resting. A light activity factor of 1.375 gives about 2060 kcal TDEE. A 400 kcal deficit target is about 1660. That is the calculator output. It is not a promise. If after a month of honest logging the scale is unchanged, you were closer to maintenance. Lower the target modestly or raise NEAT (walks, cooking more, less sitting). Do not drop to 1200 because a forum said so.

Protein at 1.6 g/kg for a 70 kg person who trains is about 112 g. The macro calculator can leave the rest to carbohydrate and fat. Then you cook lentils and chicken instead of arguing about the equation.

Keep Food Safe while you cook: the energy budget does not exempt you from 165 °F poultry. Hungry people undercook. Use a thermometer. Eat. Then log.

Questions

Sources

• Mifflin-St Jeor equation (PubMed 2305711)
• Dietary Guidelines for Americans
• USDA FoodData Central
• FDA, Nutrition Facts Label
• USDA, Keep Food Safe