The Three Layers of Daily Burn
Your total daily energy expenditure (TDEE) stacks three components: basal metabolic rate, the ~60–70% spent keeping you alive; the thermic effect of food, about 10% burned digesting; and physical activity, the layer you control most directly.
BMR is largely set by lean mass: muscle, organs, and bone. That's why two people of identical weight can burn hundreds of calories differently per day.
Metabolic Adaptation Is Real
When you cut calories hard, the body defends: thyroid output dips, movement economy improves, and hunger hormones rise. Large deficits can suppress daily burn by 10–20% beyond what weight loss alone explains.
The antidote is a moderate deficit, 15–20% below TDEE, combined with resistance training and high protein, which together preserve the lean mass that keeps metabolism high.
Habits That Move the Needle
Lift weights 2–3 times weekly, eat 1.6 g protein per kg, sleep 7–9 hours, and walk more, non-exercise activity often differs by hundreds of calories between people of similar size.
Track the trend: if weight stalls for 3–4 weeks at a given intake, that intake is your new maintenance, recalculate and adjust by 100–200 kcal, not by panic.
Sources
FAQ
What is a fast metabolism?
A higher BMR than expected for your size and age, mostly explained by more lean mass, not genetics alone.
Does dieting permanently slow metabolism?
No — adaptive thermogenesis fades as you return to maintenance, though the lower burn from simply weighing less is permanent.
How do I speed up my metabolism?
Build muscle, eat enough protein, sleep, and stay active, the levers are boring but they're the only ones that work.
Important disclaimer: Results are educational estimates, not a substitute for professional advice. Review your numbers with a qualified advisor before acting on them.