How much energy do I need?

First the app estimates your resting energy expenditure, the energy your body uses at rest. It uses the Mifflin-St Jeor formula.^[1]

• Male: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5^[1]
• Female: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161^[1]
• Not stated: the same calculation with −78 at the end. This is the mean of the two constants and our own choice, not part of the study.^[1]

The app then multiplies this value by a factor for your everyday life.

The factors lie within the ranges from FAO, WHO and UNU: 1.40 to 1.69 for sedentary or light activity, 1.70 to 1.99 for active and 2.00 to 2.40 for vigorously active.^[2] EFSA uses 1.4, 1.6, 1.8 and 2.0.^[6] Our middle levels are deliberately lower. This is our own choice.

For sport on four to five days a week, the German consumer advice centre adds 0.3.^[3] The app adds 0.2. An analysis of 1,754 adults found that on average 28% of the extra energy burned is saved again in basal expenditure.^[5] Deriving 0.2 from this is our own choice.

Example: female, 40 years, 170 cm, 70 kg, partly sitting. Resting expenditure is 1,401.5 kcal. Times 1.5 gives about 2,100 kcal. The app shows this as 1,900 to 2,300 kcal.^[1]

The formula comes from measurements of 498 healthy people aged 19 to 78.^[1] In a systematic review it fell within 10% of the measured value more often than other common formulas. The authors still warn of notable errors for individuals. Older adults and ethnic minorities in the US were underrepresented in the studies.^[4]

The estimate is a guide. If you know your needs better, enter them yourself. What you can do with it is explained in What a calorie deficit means. Why the result is a range is explained in Why the app shows ranges.