What is TDEE and why does it matter for weight management?
Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in 24 hours — including basal metabolism (BMR), physical activity, digestion (thermic effect of food), and non-exercise movement like walking and fidgeting. TDEE is the most important number for weight management: eat below it to lose fat, at it to maintain weight, or above it to gain muscle. A 70 kg moderately active adult has a TDEE of roughly 2,200–2,500 kcal/day.
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories you burn at complete rest — just to keep your heart beating, lungs breathing, and organs functioning. It represents about 60–70% of TDEE. TDEE multiplies BMR by an activity factor: Sedentary (desk job, no exercise) = BMR × 1.2; Lightly active (1–3 days/week) = BMR × 1.375; Moderately active (3–5 days/week) = BMR × 1.55; Very active (6–7 days/week) = BMR × 1.725; Extra active (physical job + training) = BMR × 1.9.
How accurate is the TDEE calculation?
The Mifflin-St Jeor equation (used here) is the most validated for estimating BMR in most populations — within ~10% of measured metabolic rate in studies. However, actual TDEE can vary ±200–300 kcal between individuals with identical stats due to genetics, muscle mass, gut microbiome, hormones (thyroid, cortisol), and NEAT (non-exercise activity). Use the calculator as a starting point, then adjust calories up or down by 100–150 kcal every 2 weeks based on actual weight change.
Does TDEE change when you diet?
Yes — metabolic adaptation (sometimes called "starvation mode") causes TDEE to drop during prolonged calorie restriction. After 8+ weeks of dieting, TDEE can fall 200–400 kcal below what the calculator predicts, due to reduced muscle mass, lower hormone levels (leptin, T3 thyroid), and unconscious reduction in NEAT. This is why weight loss slows over time. Diet breaks (returning to maintenance calories for 1–2 weeks) and resistance training help mitigate adaptive thermogenesis.
How do I use TDEE to lose weight safely?
Calculate your TDEE, then create a moderate deficit: 250–500 kcal/day below TDEE targets 0.25–0.5 kg of fat loss per week — fast enough to see results, slow enough to preserve muscle mass. Track your weight daily and take a weekly average; if you are not losing 0.25–0.5 kg per week after 2 weeks, reduce calories by 100 kcal. Pair the deficit with 0.7–1.0 g protein per pound of bodyweight and resistance training to maximise fat loss vs. muscle loss.