I would wager that just paying attention to, and thinking about what someone eats has a decent impact on their health - so it feels like it's working, and like your estimates are accurate.
After all - once you started doing it, you started losing weight/building muscle/achieving whatever result.
Yes, the mere act of monitoring (including self-monitoring) leads to behavioral change.
This alone can be sufficient for some people.
Which is a reason why keeping a food diary is an often recommended technique for changing your diet and eating healthier.