The best thing to eat before your larger meal begins is a handful of mixed nuts and seeds. Eat these 10 minutes before you begin the main course. They will be high in both fat and protein, and fat and protein will slow down the digestion of the carbohydrates in the main course so that you don’t experience sharp insulin spikes, which is what you want. They will also increase satiety so that you end up eating less.
The worst thing to eat first is bread. That will do the opposite — cause a tremendous insulin spike and make you eat even more than you need to.
So get into the habit of first eating a handful of mixed nuts and seeds when you sit down to eat — before anything else.