The best diet is the one you don’t know you are on.
I am not surprised to read this:
When eating in group of four or eight, light eaters ate more, and heavy eaters ate less.
Those are both from Brian Wansink’s Mindless Eating: Why We Eat More Than We Think.
Here is a New York Times article about the book; it summarizes the book’s practical tips. Never let yourself forget how much you are eating. You might also use smaller bowls and wrap transparent candy containers in aluminum foil.