In FatLand (I): The Novel, the issue of mortality in FatLand, as opposed to the Other side, is explored. It starts to embarrass someone who has an ax to grind that FatLand's mortality rate is actually now lower than that of the Other Side.
Why? Well, many reasons. First of all, the stress level just in itself is much, much lower in FatLand. And many studies now show that the same symptoms and illnesses that are correlated with supposed fatness are also correlated with high stress levels. So guess what: when the stress goes, the illnesses either leave or appear in much less severe forms. And this goes for people of any weight. But it goes double for fat people because not only does stress make them feel sick, literally, but it deters them from doing things like moving their bodies and eating happily (i.e., they don't get the nutrition from their food that they should). In FatLand, where people can now move without being harassed and can eat without someone looking suspiciously at everything they eat, stress is further reduced for them.
Secondly, as stated elsewhere, the economiic safety net is very strong - payment during periods of unemployment, counseling and job matching service, single payer health insurance coverage. For everyone. A lot of stress is removed when one knows that her or his family won't starve if unemployment occurs and that a job will come along in not too long.
And of course the person with the ax to grind is none other than Winston Stark :) He can't stand the fact that his CompleteFitness franchises failed in FatLand, so he is doubly disgusted when Sandor Forman's GymNotTrim franchises take off and are wildly successful and provide opportunities for FatLanders to move and play without worrying about their weight.
Winston Stark stresses over this and many other things pertaining to FatLand, counting the time until his plans can come to fruition..