FWIW, I lost 10 lbs a few years ago by reducing portion sizes. I saw some dude on tv talking about how to lose weight, and he mostly he just said "I"ll tell you an important secret after this commercial," but I did manage to hear secret #1 which was eat when you fell physically hungry and stop eating as soon as you start to feel full.

It made sense, since so many people eat for other reasons, like boredom and emotions, and many were probably taught (like me) to always eat everything on their plates when they were growing up.

So instead of eating a whole sandwich for lunch, even though I was full before I finished it, I would eat half and put the other half in the fridge. Then instead of a late afternoon snack, I would eat the other half of the sandwich.

For dinner, I started making smaller portions for the same reason -- I was always full before I finished eating, so I figured I didn't need to eat so much.

Anyway, even doing this it helps to focus on healthier foods and stuff like that, but I did find it helpful.