Note: Once you delete the start weight entry you won't be able to edit it or change the start weight. Then the next weight entry will automatically become your start weight.

It is not possible to change the date for a weight entry, just the weight on a specific date

- Click on Profile (you get there by clicking on the profile icon in the middle of the bottom tab bar in in the Diary) 
- Then choose Body in the Profile view
- Tap on the button Track body measurements
- Tap on Current in the weight section. In this view you can see the history of your weight. Scroll down till you see the first tracked weight - your start weight
- Tap on the number and change it to the desired amount.
- Confirm by tapping 'Save
- Check your weight tracker: your start weight is now updated

Alternatively, if you want to set a completely new start weight, please choose a new goal.