Calorie Deficit Formula
Daily deficit needed = (lbs to lose × 3,500) / days
Daily calorie target = TDEE − daily deficit
Safe range: deficit of 300–750 cal/day
Rate of Loss Guide
| Daily Deficit | Weekly Loss | Assessment |
|---|---|---|
| 250 cal/day | 0.5 lb/week | Conservative — very sustainable |
| 500 cal/day | 1 lb/week | Standard — widely recommended |
| 750 cal/day | 1.5 lb/week | Aggressive but manageable |
| 1,000 cal/day | 2 lb/week | Max recommended; hard to sustain |
| 1,500+ cal/day | 3+ lb/week | Not recommended — muscle loss risk |
Frequently Asked Questions
Is the 3,500 calories = 1 lb rule accurate?
It is a useful approximation but not perfectly accurate. Actual weight loss is more complex — as you lose weight, your TDEE decreases (you have less body mass to move). Hormonal adaptation, water retention changes, and metabolic adaptation mean results slow over time. The rule is accurate enough for short-term planning but expect to re-calculate every 4–6 weeks as your weight changes.
What is the minimum safe calorie intake?
Most guidelines suggest no lower than 1,200 calories/day for women and 1,500 calories/day for men for general nutrition adequacy. Going below these levels significantly increases risks of nutrient deficiency, muscle loss, gallstones, and metabolic adaptation. Medically supervised very-low-calorie diets (VLCD, 800 calories) are sometimes used short-term.
Why am I not losing weight at a 500-calorie deficit?
Common reasons: underestimating food intake (studies show people underreport by 20–50%), overestimating exercise calories, water retention masking fat loss, metabolic adaptation, or your TDEE estimate being off. Track food precisely for 2 weeks before concluding the deficit isn't working. Weight also fluctuates ±3–5 lbs daily from water alone.