A 1998 Gallup Poll showed that 64 % of U.S. residents pray before eating meals, but 1998 was quite a long time ago. I can recall observing a family or two saying Grace before eating at various restaurants, but judging by the sideways glances, it wasn't considered "normal".
As an atheist, I actually enjoy the practice. Not as a way to thank a Being, but a moment to be generally grateful for being fortunate enough to have sustenance, the means to provide sustenance, and the company in which you get to enjoy the sustenance.
In this very busy and "go! go! go!" lifestyle (which I personally believe contributes to overeating), I think stopping to reflect on your food can give you a sense of calm, a reality-check so to speak.
Here are some examples of Grace:
Catholic. (before eating) Let us pray. Bless us, O Lord, and these, Thy/Your gifts, which we are about to receive from Thy/Your bounty. Through Christ, our Lord. Amen.
Lutheran. (before eating) Come, Lord Jesus, be our Guest, and let Thy/these gifts to us be blessed. Amen.
Jewish. (after eating) There are separate blessings for fruit, vegetables, non-bread grain products, and meat, fish, and dairy products, but a meal is not considered to be a meal unless bread is eaten. Saying grace after the meal is derived from Deuteronomy 8:10: "And thou shalt eat and be satisfied and shalt bless the Lord thy God for the goodly land which he has given thee."
Islamic. (before eating) Thank you, oh Allah, for feeding us and making us amongst the believers.
Hindu. (before eating) The act of offering is God (Brahma), the oblation is God, By God it is offered into the fire of God, God is That which is to be attained by him who sees God in all.
Buddhist. (before eating) In this food I see clearly the presence of the entire universe supporting my existence. I am aware that each morsel is the fruit of much hard work by those who produced it.