Calorie Deficit Calculator: Sustainable Weight-Loss Pace
Calculate a sustainable daily calorie deficit from your resting energy and movement, with built-in adult safety guardrails and protein preservation targets.
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How to choose a sustainable daily calorie deficit
Crash diets fail because aggressive deficits trigger disproportionate hunger, lean-mass loss, and adaptive thermogenesis. Mira defaults to a −500 kcal/day moderate deficit (with presets from −200 to −700 kcal/day and a custom range up to −1,000 kcal/day), clamped at a 1,200 kcal/day adult floor and blocked when BMI is below 18.5 kg/m².
| Daily Deficit Pace | Initial Weekly Pace (Wishnofsky) | Best Suited For |
|---|---|---|
| −300 kcal / day | ~0.25 kg / week | Gentle recomposition, active training schedules, or smaller maintenance budgets |
| −500 kcal / day (Default) | ~0.45 kg / week | Evidence-based adult baseline balancing steady progress with muscle retention |
| −700 kcal / day | ~0.60 kg / week | Higher maintenance budgets (>2,300 kcal/day) with strong protein and fiber intake |
Why initial weight change differs from long-term adaptation
In the first 7–14 days of a calorie deficit, stored muscle and liver glycogen declines alongside bound water (~3 g of water per gram of glycogen), causing a faster initial drop on the scale. Over subsequent months, as body mass decreases, resting and movement energy expenditure gradually adapt downward (Hall et al., 2011).
Three rules for preserving lean mass in a deficit
- Prioritize protein: Aim for roughly 1.2–1.6 g of protein per kg of body weight (or select Mira’s High protein 40/35/25 preset).
- Keep fiber at or above 25 g/day: High-volume vegetables, legumes, and whole grains stretch gastric volume without adding excess energy.
- Include resistance movement: Two to three weekly strength sessions signal your body to retain skeletal muscle while drawing on fat stores.
Scientific references & editorial attribution
Authored and maintained by the Mira Team (Friction Ventures GmbH, Switzerland):
- Hall et al., 2011: Quantification of the effect of energy imbalance on bodyweight (The Lancet)
- Wishnofsky, 1958: Caloric equivalents of gained or lost weight
- Mifflin et al., 1990: A new predictive equation for resting energy expenditure in healthy individuals
- Morton et al., 2018: Protein supplementation and resistance training-induced gains in muscle mass and strength