Daily Calorie Needs: BMR, TDEE & Deficit Planning

Profile

BMR

M 25y 170cm 65kg

1,593 kcal

M 40y 172cm 75kg

1,630 kcal

F 25y 160cm 52kg

1,234 kcal

F 40y 162cm 60kg

1,252 kcal

Key Takeaways

BMR (Mifflin): men = 10w + 6.25h − 5a + 5; women = 10w + 6.25h − 5a − 161

TDEE: BMR × activity — sedentary 1.2, light 1.375, moderate 1.55, heavy 1.725, athlete 1.9

Fat loss deficit: 300–500 kcal/day below TDEE ≈ 0.5kg/week; never eat below BMR long-term

Protein target: 1.2–2.0g per kg body weight during a deficit to preserve muscle

Core answer: Daily calorie needs = BMR × activity factor (TDEE), then adjust for your goal: fat loss = TDEE − 300~500 kcal (≈0.25–0.5 kg/week), muscle gain = TDEE + 200~300 kcal. A sedentary 30-year-old, 70 kg, 175 cm man: BMR ≈ 1,650 → TDEE ≈ 1,980 (×1.2); moderate exercise 3–5×/week → ≈ 2,560. A 55 kg, 160 cm woman: BMR ≈ 1,250 → TDEE ≈ 1,500–1,940. Never diet below 1,200 (women) / 1,500 (men) kcal without medical supervision.

The activity factors (honest version)

Lifestyle	Factor	Example
Sedentary (desk, no exercise)	×1.2	most office workers
Light (walks, 1–3 workouts/wk)	×1.375
Moderate (3–5 workouts/wk)	×1.55	regular gym-goer
Very active (physical job + training)	×1.725
Athlete (2× daily training)	×1.9	rare

Reality check: wearables show most "I exercise a lot" office workers burn closer to ×1.3–1.4. Overestimating activity is the #1 reason diets "don't work".

The deficit math

1 kg of body fat ≈ 7,700 kcal. A 500 kcal daily deficit → ~0.45 kg/week, ~1.8 kg/month. Larger deficits cost muscle, energy, and adherence — 10–25% below TDEE is the sustainable band.

Worked examples

Example 1 — Fat loss, male. TDEE 2,400 → eat 1,900–2,000 kcal, protein ≥1.6 g/kg (112 g at 70 kg). Expect −0.4 kg/week; after 12 weeks ≈ −5 kg with strength largely preserved.

Example 2 — Fat loss, female. TDEE 1,800 → eat 1,400–1,500 kcal. Note the floor problem: a 500-deficit from a small TDEE hits the 1,200 floor fast — shrink the deficit to 300 and accept −0.25 kg/week, or raise TDEE by moving more.

Example 3 — The weekend wipeout. Weekday deficit 500 × 5 = −2,500 kcal; Saturday dinner + drinks +3,500 kcal → net weekly surplus. Weekly totals, not daily heroics, decide results.

Example 4 — Adaptive reality. After losing 5 kg, BMR drops (~15 kcal/kg) plus the body moves less (NEAT adaptation): your old TDEE is now ~150 kcal lower. Recalculate every 4–6 weeks or progress stalls.

Common mistakes and myths

Eating back exercise calories — trackers overestimate burn by 20–50%; eat back at most half of what the watch says.
Crash deficits — 800 kcal diets lose muscle and rebound; the research sweet spot is boring: 10–25% deficit + protein + resistance training.
Ignoring liquid calories — a daily latte + milk tea + juice adds 400–700 kcal that never feels like "eating".
"Starvation mode" — metabolism adapts modestly (5–15%), it doesn't stop; stalls are usually miscounting, not broken physiology.
Precision theater — labels allow ±20% error; hitting ±100 kcal daily is fantasy. Aim for consistent ranges and judge by the 2-week weight trend.

Frequently Asked Questions

How do I calculate my daily calorie needs?

Two steps. First BMR (Mifflin-St Jeor): men = 10×weight + 6.25×height − 5×age + 5; women same but −161. Then multiply by activity: sedentary 1.2, light exercise 1.375, moderate 1.55, heavy 1.725. A 30yo man, 70kg, 175cm, sedentary: BMR ≈ 1,618 → TDEE ≈ 1,940 kcal.

How big a deficit do I need to lose weight?

300–500 kcal/day below TDEE gives 0.25–0.5kg loss per week — the sustainable range. Aggressive 1,000+ kcal deficits cause muscle loss, metabolic adaptation and rebound. Women should not go below ~1,200 kcal, men ~1,500 kcal, without medical supervision.

Which activity factor should I pick?

Sedentary (desk job, no exercise): 1.2. Light (walking or sports 1–3 days/week): 1.375. Moderate (3–5 days/week): 1.55. Heavy (6–7 days or physical job): 1.725. Most people overestimate — when in doubt, pick the lower factor and adjust after 2–3 weeks of scale data.

Why did my weight loss stall after a few weeks?

Three main causes: (1) your TDEE dropped with your weight — recalculate every 5kg lost; (2) metabolic adaptation cuts NEAT (fidgeting, daily movement) by 100–300 kcal; (3) logging drift — portions creep up. Fix: recalculate TDEE, add a 1–2 week diet break at maintenance, tighten food logging.

How much protein do I need while cutting?

1.2–2.0g per kg body weight (up to 2.2g/kg for lean, training individuals). For 70kg that is 84–140g/day. High protein preserves muscle in a deficit, increases satiety, and costs more energy to digest (thermic effect ~25% vs ~5% for fat). Spread across 3–4 meals.

Should I eat back exercise calories?

Only partially — trackers overestimate burn by 20–50%. If you set your activity factor honestly, exercise is already included, so do not eat it back. If you use a sedentary factor plus logged workouts, eat back 50–70% of estimated burn. The scale trend over 2 weeks is the only reliable judge.