To lose weight, a person must consume fewer calories than the body burns. The size of that gap, called the calorie deficit, determines how fast weight changes. A deficit of 500 calories per day produces about 0.5 kg (1 lb) of fat loss per week, because 1 kg of body fat stores roughly 7,700 calories. This article shows how to calculate a daily deficit from a maintenance estimate and a chosen weekly loss rate, and how to adjust when progress stops.

Step 1: Estimate Maintenance Calories from Body Weight and Activity

Maintenance calories are the daily intake that keeps body weight stable. The most practical starting point uses body weight in kilograms multiplied by a factor based on usual activity. A sedentary person (desk work, minimal walking) needs about 30–32 kcal per kg per day. A moderately active person (walks 30–60 minutes or has a physical job) needs about 33–37 kcal per kg. A highly active person (daily training or heavy labor) needs about 38–42 kcal per kg.

Example: a 70 kg adult with moderate activity has a maintenance estimate of 70 Γ— 35 = 2,450 kcal per day. This figure is an estimate, not a fixed truth. If the person has tracked intake and weight for two weeks, the actual maintenance can be refined: average daily intake plus (weight change in kg Γ— 7,700 Γ· 14). For a 70 kg person eating 2,300 kcal daily and losing 0.3 kg per week, maintenance is 2,300 + (0.3 Γ— 7,700 Γ· 7) = 2,630 kcal.

Step 2: Choose a Weekly Loss Rate and Convert to a Daily Deficit

Select a target weekly weight loss based on body fat percentage and comfort. A safe rate is 0.5–1% of body weight per week. For a 70 kg person, this equals 0.35–0.7 kg per week. A 0.5 kg weekly loss requires a daily deficit of 0.5 Γ— 7,700 Γ· 7 = 550 kcal. A 0.7 kg weekly loss requires 770 kcal per day.

Set the daily intake as maintenance minus the deficit. Using a maintenance of 2,450 kcal and a 550 kcal deficit gives 1,900 kcal per day. For a 770 kcal deficit, intake becomes 1,680 kcal per day. Intakes below 1,200 kcal for women or 1,500 kcal for men present challenges for nutrient adequacy and muscle retention without medical supervision.

Step 3: Verify the Deficit with Food Labels and Portion Weights

Track actual intake for one week using a food scale and nutrition labels. Weigh cooked portions separately from raw ingredients. For mixed dishes, enter each component individually. Record every snack, drink, oil, sauce, and condiment. Compare the average daily intake to the calculated target. If the tracked intake is 300 kcal above target, reducing portion sizes or replacing high-calorie items, instead of skipping meals, maintains nutritional balance.

Use a weekly average rather than a single day. Daily fluctuations from water, sodium, and glycogen make one-day weigh-ins unreliable. Weigh every morning after using the bathroom and before food, then average seven days. Compare the weekly average to the previous week to assess the true rate of change.

Step 4: Adjust for Plateaus and Metabolic Adaptation

A plateau is defined as no change in the weekly average weight for 2–3 weeks while intake and activity remain consistent. The first response is to recalculate maintenance using the tracked data. If a 70 kg person has been eating 1,900 kcal and losing 0.4 kg per week, actual maintenance is 1,900 + (0.4 Γ— 7,700 Γ· 7) = 2,340 kcal. The deficit is 440 kcal, not the planned 550.

To restore the original deficit, lowering intake by 110 kcal per day (the difference between planned and actual deficit) or increasing activity by roughly 20 minutes of brisk walking works. Another option is to accept a slower loss rate if the deficit is still positive. A true stall with zero weight change over three weeks suggests the maintenance estimate is too low or intake tracking has errors; recheck portion sizes and hidden calories.

Step 5: Use Body Measurements and Strength as Secondary Signals

Scale weight can stay flat while body composition improves. Measure waist circumference at the navel and hip circumference at the widest point once per week. A reduction of 1 cm in waist with no scale change indicates fat loss and water retention. Track strength in main lifts or push-up repetitions; if strength holds or increases, muscle loss is unlikely.

If the waist is shrinking but the scale is not, keeping the current intake for another two weeks is appropriate. If both waist and scale are unchanged for three weeks, reducing intake by 5% (about 95–125 kcal for most people) or increasing daily steps by 2,000 restores progress. Recheck after two weeks before making another change.

Checklist for Calculating and Adjusting a Daily Calorie Deficit

1. Estimate maintenance using body weight in kg times an activity factor (30–42 kcal/kg).
2. Refine maintenance from two weeks of tracked intake and weight change using the formula: average intake + (weekly weight change Γ— 7,700 Γ· 7).
3. Choose a weekly loss rate of 0.5–1% of body weight and convert to a daily deficit by multiplying the kg loss by 7,700 and dividing by 7.
4. Set daily intake = maintenance βˆ’ deficit, keeping it above 1,200 kcal for women and 1,500 kcal for men.
5. Track all intake with a scale and labels for one week; compare the average to the target.
6. If the weekly average weight is unchanged for 2–3 weeks, recalculate maintenance from actual data and adjust intake down by 100–150 kcal or add 2,000 steps.
7. Use waist circumference and strength performance as secondary checks when the scale is not moving.