BMR and Weight Loss: How Your Resting Calories Shape Diet Targets — 2026

Basal Metabolic Rate (BMR) is the calories your body burns at complete rest to keep you alive — breathing, circulation, and cell repair. Total Daily Energy Expenditure (TDEE) adds the energy of daily activity, digestion, and exercise. BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + s, where s is +5 for men and −161 for women. This Mifflin–St Jeor equation is the most validated modern formula.

Multiply BMR by an activity factor to estimate TDEE. A moderate deficit below TDEE (about 10–20%, or roughly 300–500 kcal/day for many adults) supports gradual fat loss while preserving muscle; a small surplus supports muscle gain.

• Sedentary (little or 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

Poor sleep and chronic stress can shift hunger hormones and, over time, nudge eating and activity patterns that change TDEE. They do not rewrite the underlying BMR formula, but they influence the real-world calories you burn and eat.

• Adults 18–64: 7–9 hours per night (AASM).
• Adults 65 and older: 7–8 hours per night (AASM).
• Consistently sleeping under 7 hours is linked to higher risks of obesity, type 2 diabetes, and cardiovascular disease.

The BMR/TDEE formulas estimate energy needs from body size and activity, not from diet composition. What changes is the calorie and protein balance around that estimate: very low-calorie or restrictive patterns can lower TDEE over time as the body adapts, so recalculate after weight changes.

BMR falls with age and with weight loss, so revisit your numbers every few months or after significant changes in weight, training, or life stage. Treat TDEE as an estimate to adjust against real-world results over weeks.