什麼是熱量赤字？安全的減脂速度

A calorie deficit is eating and drinking fewer calories than your body burns in a day, which forces it to draw on stored fat (and some lean tissue) to make up the difference. Your body burns calories through basal metabolism, digestion, and activity combined, known as total daily energy expenditure (TDEE); when intake is consistently below that number, weight goes down over time, and when it is above, weight goes up.

A safe calorie deficit is generally 300 to 750 calories per day below your maintenance level, which produces roughly 0.5 to 1.5 pounds (0.25 to 0.7 kg) of loss per week for most adults without excessive muscle loss or metabolic slowdown. Deficits beyond about 1,000 calories a day, or intakes under roughly 1,200 calories for women and 1,500 for men, raise the risk of nutrient shortfalls, fatigue, and muscle loss, and are not recommended without individualized guidance.

The size of the deficit needed depends on how much and how fast you want to lose: a 500-calorie daily deficit targets about 1 pound per week, since roughly 3,500 calories equals one pound of fat, while a smaller 250-calorie deficit targets a slower, more muscle-sparing 0.5 pounds per week. Larger people and those with more body fat to lose can typically sustain a bigger deficit (closer to 750 to 1,000 calories) than leaner individuals, who should stay conservative to protect lean mass.

Yes, because men generally have higher lean mass and TDEE, a given percentage deficit translates to more absolute calories for men than for women, and the recommended calorie floors differ too, commonly cited as roughly 1,500 calories per day for men and 1,200 for women as a minimum before micronutrient and energy needs become hard to meet. Age matters as much as sex: TDEE declines gradually after the 30s and 40s as lean mass and activity tend to drop, so the same fixed deficit becomes proportionally larger later in life.

The only reliable way to confirm a deficit is working is to track body weight over 2 to 4 weeks and look at the trend line rather than any single day, since daily weight swings 2 to 5 pounds from water, sodium, and digestion and can mask real fat loss or gain. A true deficit shows up as a gradual downward trend of roughly 0.5 to 1.5 pounds a week; if weight is flat or rising over several weeks despite logged intake looking correct, the estimated TDEE was probably too high and the actual deficit needs to be recalculated from the trend, not assumed from the math.