# Why the app gives no target date

Many calculators give you a date and a number of kilos. The app does not, because weight does not behave that way.

## The old rule of thumb falls short

A common claim: about 2 MJ less a day, roughly 480 kcal, means a steady 0.5 kg less per week. According to Hall and colleagues, this is wrong. The rule ignores that expenditure changes with body weight.[^1]

## Weight responds slowly

In Hall's model, half of a weight change is reached after about 1 year and 95% after about 3 years. People with more body fat take longer to reach a new balance.[^1]

This applies to an average adult with overweight and to a change that lasts.[^1] For one person, it is not a prediction.

## Single days say little

An analysis of 4,657 measurements from 80 adults found a weekly rhythm: weight was higher on Sunday and Monday and fell during the week. The authors consider such changes normal.[^2]

## What the app shows instead

The app shows what you entered and, for weight, a mean value if you want one. It names no date and no kilos you will reach.

## Sources

[^1]: [Hall KD et al.: Quantification of the effect of energy imbalance on bodyweight. Lancet, 2011](https://pubmed.ncbi.nlm.nih.gov/21872751/)
[^2]: [Orsama AL et al.: Weight rhythms: weight increases during weekends and decreases during weekdays. Obes Facts, 2014](https://pubmed.ncbi.nlm.nih.gov/24504358/)

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Last updated: November 2026. This is general information and not medical advice.

Original article: https://kostenlos-abnehmen.de/en/wissen/keine-prognose