Many medical facts" are simply not true. By definition, being "overweight" must be bad for your health - or we wouldn't call it overweight. But we do not define overweight as being the weight above which you are damaging your health; it has an exact definition. To be overweight means having a BMI of between 25 and 30. In 2009, a German group did a painstaking meta-analysis of all studies on overweight and obesity that they could find. As with most other researchers, they found that being overweight was good for you. Of course, they didn't phrase it in this way. They said: "The prevailing notion that overweight increases morbidity and mortality, as compared to so-called normal weight, is in need of further specification." In need of further specification? An interesting phrase, but one that hints at the terrible problems researchers have when their findings fail to match prevailing dogma; if the prevailing consensus is "if your BMI is between 25 and 29, it is damaging your health and you should lose weight", then you challenge this at your peril. Despite the fact that study after study has demonstrated quite clearly that "overweight" people live the longest, no one can bring themselves to say: "Sorry, we were wrong. A BMI between 25 and 29 is the healthiest weight of all. For those of you between 20 and 25, I say, eat more, become healthier." Who would dare say such a thing? Not anyone with tenure at a leading university, that's for sure.