Not just by uglying up the place, but through global warming. Don't take my word for it -- just ask these guys from the "London School of Hygiene and Tropical Medicine"! It turns out that all of us Fatty McFattersons could save the planet, if only we didn't insist on being so fat. Fortunately some other bloggers were on top of this and have pretty much skewered it, so I'll just direct you to them: Fillyjonk over at Shapely Prose brings the snark; CarrieP at Big Fat Blog gives another good analysis and points out that for their calculations, the "researchers" assumed that fat people drive bigger cars (!).
As a follow-up to the United Airlines post, in case you're interested, here's a petition you can sign that will be sent to United telling them it's not OK for them to have their gate agents size people up and make them pay double to fly as punishment for being fat. Part of United's justification for their newly articulated policy was that they received 700 complaints from people who felt inconvenienced by having to sit next to a fat person. So the goal of the petition is to show United that their new policy is going to piss off a lot more than 700 people (there was another similar petition on PetitionOnline that had already reached 700 signatures, but sadly someone hacked it and managed to get it deleted from the site before the owner was able to compile everything to send to United).