I used to think this was a good alternative to saying I was on a low carb diet. Until I realized that inevitably at some point I will decide to have something with sugar or gluten in it as a rare treat. I don't want to be given the hairy eyeball. I do tell friends/family/coworkers that too much gluten or sugar gives me problems like gas, itchy skin, insomnia, irritability and weight gain and that it's best if I don't eat it. This is the truth. I don't feel guilty about saying no thanks and most people don't challenge me.