I always tip fat servers and delivery drivers less. Normally I tip servers 20%. If my server is fat I cut it down to 10%.  Harder to do with delivery people, but if I get a good look at them before they can see my money I will put a couple dollars back into my pocket. I don't know exactly why I do it, I guess it is because I hate fat people. I encourage you all to do the same! I don't have the balls to completely stiff the fats even though I have considered it I have never followed through.