This is really interesting, and I'll probably sign up for your app (I'm training for rock climbing). I've used a kitchen scale for a few weeks at home and got pretty good at estimating portion size during that time. Biggest takeaway was that even if you aren't "over-indulging" when you eat out, the portion sizes (especially in the US, less so in Europe) are just insane. 2-3x portions. Ordering half-orders or starters and letting the food settle before eating/ordering more helped quite a bit.