Food budget question

Out of all the budget’s I make, our food budget is always the hardest. I put money away for it every two weeks but I never seem to get it right. And most of the time I am short. I have two boys ages 14 and 11 who eat almost non stop when they are home. Does anyone have any pointers to share with me (besides adding more to that budget) on how to get this right?

I’ve been keeping track of how much I spend each month on food for a couple of years now. And each month it runs anywhere from $450 to $750 a month.