Compute daily energy deficit for fat loss (about 7700 kcal per kg of fat).
按 1 kg 脂肪 ≈ 7700 kcal 的能量守恒推算：先由总能耗除以天数得每日缺口，再按设定比例拆分为饮食减少与运动消耗两部分，并依减重速率给出安全性与建议。
| Item | Formula / Rule | Source / Standard |
|---|---|---|
| Energy deficit definition | Energy deficit equals energy expenditure minus energy intake; a negative balance is a deficit. | Hall KD et al. 2011, The Lancet - quantitative physiology of weight loss |
| Rate of weight loss | A daily deficit of 500 to 1000 kcal corresponds to losing about 0.5 to 1 kg per week. | ACSM's Guidelines for Exercise Testing and Prescription, 11th ed. (2021) |
| Total energy expenditure | Total daily energy expenditure is basal metabolic rate multiplied by an activity factor. | Mifflin MD et al. 1990 & ACSM 2021 |
基于 1kg 体脂约含 7700 kcal 能量的原理，结合目标减脂量与时间周期，计算每日所需热量缺口，并按饮食与运动比例拆分，附运动时长建议。