I’m working up the state level statistical COVID19 model to conclude the series on COVID19 non-pharmaceutical work arounds, and the numbers regarding obesity and COVID19 mortality gave me unexpectedly complicated results. The conventional wisdom is that obesity increases COVID19 mortality, but the data show yes but also no.
Turns out the research has already been done on the general subject. Being too skinny is not good, and being much too fat is also not good. See the graph below. And -- in older people — this is the case for all causes of death.
I suspect this works because fat cells secrete visfatin — which is the extracellular form of NAMPT, an enzyme critical to the operation of the cellular NAD salvage cycle, a series of chemical reactions that takes waste nicotinamide and converts it back to the NAD form that is used for generating cellular energy. Perhaps extracellular visfatin produced by body fat is imported into cells and ends up incrementally increasing the NAD resources of the moderately obese. This is hypothesizing, as the research I’ve read on visfatin function seems primarily concerned about its effect on insulin resistance and inflammation. No one in the research world evidently has yet explored the possibility that increasing body fat with age is also a homeostatic development that extends human life span (at the cost of some inflammation and increased insulin resistance).