It's frowned upon to refuse food that someone offers.
Brad is on a diet, but he's over at a house party and his friend Ted offers him a homemade cookie.
Brad wants to lose weight.
Brad accepts a cookie and goes for a run later to make up for it.
Brad pushes the cookie away and refuses to eat it.
Ted feels happy that Brad enjoyed one of his homemade cookies.
Ted is a little offended and hurt thinking that Brad doesn't find the cookie appetizing.