Not defending over eating and not exercising (people NEED to eat correct portions of GOOD NUTRITIOUS  food and exercise regularly with enough intensity to work up a good sweat) but this did happen to me.  I once carried around 39 extra pounds and was sick all the time.  Doctor's took blood tests and told me I was fine.  I went to a naturopath who took a stool sample and found I had casein antibodies meaning my immune system was attack my food.  At that time, I was eating a lot or probiotic yogurt.  Once I cut out all dairy, my skin cleared up and weight just started falling off.  I had more energy and started running again and lost about a pound a day.  On the follow up visit the naturopath explained to me that when your immune system is fighting a losing battle, it will force things out of your skin and if it is still over burdened, it will store crap in fat cells to deal with later.  As soon as my immune system no longer needed to deal with everything I ate, it went I to clean up mode and got rid of the fat that was storing more of the casein.  Having said all of that, it won't make a world of difference to fat fucks, they're too lazy to go out and get a correct diagnosis.  Their bodies seem like they're working against them, but garbage in equals garbage out and the don't want to hear that they would have to give up ice cream, pasta, pizza and everything else that has milk ingredients in them.  Fuck you could give the fat fucks an actual diagnosis and they would still say it's because of their genetics.