Here's one way to eat less that I personally don't use, but which works well for some people:

stop eating at night.

The idea is that you can eat anything you want and as much as you want during the day. Once the witching hour arrives, stop eating. It's common to set the time an hour or two before bedtime.

This is a great tactic because it's simple and straightforward. It's literally the One Rule embodied. For those who don't mind missing out on nighttime gatherings, this works very well.

I know someone who uses this trick every couple of years to lose anywhere from thirty to fifty pounds. (It's not a very healthy situation to gain and lose that much weight so often, but that's another story.)

When he decides it's time to lose weight again, he stops eating at six o'clock every night. He typically wakes up at around five in the morning to go to work, so that's about eleven to twelve hours of not eating every day. Breakfast becomes the most enjoyable meal of the day in this situation.

Personally, I don't use this tactic very often because it can get awkward socially. I usually end up making exceptions for certain occasions. Afterwards, I have trouble getting caught up with the missed night. I find that working with a week long timeframe gives me the flexibility to plan ahead or cram from behind as needed.