Average TDEE by Age, Sex, and Activity Level

Average TDEE for US adult males (20-39): 2,600-2,800 kcal/day

Based on moderate activity level. Sedentary males average 2,200-2,400; very active males can exceed 3,200.

Average TDEE for US adult females (20-39): 2,000-2,200 kcal/day

Based on moderate activity level. Sedentary females average 1,800-2,000; very active females can exceed 2,600.

BMR accounts for 60-75% of total daily energy expenditure

The largest component of TDEE is involuntary — organ function, breathing, circulation. Exercise typically adds only 15-30% of total burn.

NEAT can vary by up to 2,000 kcal/day between individuals

Non-exercise activity thermogenesis — fidgeting, walking, posture — is the most variable component of TDEE and the hardest for formulas to predict.

Mifflin-St Jeor predicts BMR within 10% for 82% of people

Making it the most accurate general-purpose BMR formula. Harris-Benedict overestimates by ~5% on average. Katch-McArdle is more accurate when body fat % is known.

TDEE declines ~1-2% per decade after age 50

Primarily due to loss of muscle mass (sarcopenia) and hormonal changes. Resistance training 2-3x/week can significantly slow this decline.

Total daily energy expenditure peaks between ages 20-35

Contrary to popular belief, metabolism doesn't crash at 30. The major decline begins after 60. The 20-60 range is relatively stable when adjusted for body composition.

One hour of resistance training burns 200-400 kcal depending on intensity

Far less than most people assume. A 1-hour lifting session adds only ~10-15% to a sedentary person's daily TDEE. The real benefit is increased BMR from added muscle mass over time.

Metabolic adaptation can reduce TDEE by 5-15% during sustained dieting

Beyond the expected BMR drop from weight loss, the body reduces NEAT and metabolic efficiency. This is the primary cause of weight loss plateaus after 8-12 weeks.

Thermic effect of food (TEF) accounts for ~10% of TDEE

Protein has the highest TEF (20-30% of calories consumed), followed by carbs (5-10%) and fat (0-3%). High-protein diets slightly increase daily calorie burn through this mechanism.

Each kilogram of muscle burns approximately 13 kcal/day at rest vs. 4.5 kcal/day for fat tissue

While the per-kg difference seems small, gaining 5 kg of muscle and losing 5 kg of fat increases resting metabolism by roughly 40-45 kcal/day.

Obese individuals have higher absolute TDEE than lean individuals at the same height and age

More body mass requires more energy to maintain — even fat tissue is metabolically active. This is why larger individuals can sustain larger deficits without going below safe minimums.

Activity multipliers (1.2-1.9) were originally derived from doubly-labeled water studies in the 1980s-90s

The multiplier categories (sedentary, lightly active, etc.) are population averages. Individual variation within each category can be 200-400 kcal/day.

Pregnant women require an additional 300-450 kcal/day above baseline TDEE in the second and third trimesters

First trimester energy needs are minimal. The additional energy supports fetal growth, increased blood volume, and maternal tissue changes.

Cold exposure can increase TDEE by 5-15% through non-shivering thermogenesis

Brown adipose tissue activation in cool environments burns extra calories, but the effect is modest and impractical as a weight loss strategy for most people.