What you burn, from the scale and the food log

Calorie apps guess what you burn from a formula: age, height, weight, an activity multiplier you pick from a list. The guess is often hundreds of calories off, and it never learns.

There’s a better source: you. If you logged what you ate and the scale moved, energy balance tells you the rest.

The arithmetic

Over the last 28 days (ending yesterday, because today isn’t over):

1. Average the calories logged per day.
2. Fit a straight line through the daily average weigh-ins. Its slope is the trend in kg per day. A least-squares line barely moves for one salty dinner, which is the point.
3. A kilogram of body mass is roughly 7,700 kcal. If the trend fell 0.5 kg a week, the body covered about 550 kcal a day from storage.

Burn = average intake − slope × 7,700. Eat 2,000 a day while losing half a kilo a week, and you burn about 2,550.

When it won’t answer

It needs 14 days of food, 8 weigh-ins, spread over at least 14 days. Below that it shows progress toward those numbers instead of a figure.

If the answer comes out under 1,000 or over 6,000 kcal, it says the food log and the scale don’t add up. That almost always means meals weren’t logged, and a wrong number on the screen would do more harm than none.

The suggestion, kept gentle

With a weight goal set, the app suggests a calorie target toward it. Every suggestion is capped:

• Losing at most 0.5% of body weight a week.
• Never more than 750 kcal below what you burn.
• Never under 1,200 kcal.
• Within a kilo of the goal, it suggests maintenance.

PaceStreak has refused calorie and diet habit templates since habits shipped, because a streak for eating less is an incentive to undereat. Nutrition arrived because people asked for it. The guard moved from “never” to these caps, and calories still never touch XP, a badge or a leaderboard.