Add the possibility to mark an entry as "junk"
Sometimes we eat things we would rather not have eaten. Sometimes or oftentimes...
It would be nice to somehow track the percentage of "junk calories" in your diet, by allowing users to mark foods as such. I've seen similar requests for "calories from animal foods" which could use the same functionality to accomplish that task.
The main point would of course be to add this as a percentage in the dashboard, so you can aim to get it lower. You could also see what impact (for example) a visit to grandma's has on your junk to healthy food ratio.