Diet is defined as 'the foods eaten, as by a particular person or group' (at least one definition). So technically, I'm on a diet. Pizza, snickers bars, and gatorade and occasionally a bowl of cereal. If you or someone you love is on a more stringent diet, you probably know how difficult it can be and how a diet t-shirt could really help! We have lots of funny diet shirts and some not funny diet shirts. Diet t-shirts make great gifts for the holidays.