Of course, it could also be that something we eat reacts with the HCl in the stomach to go BOOM!! Or maybe, every time you eat something, you ingest tiny,cloaked aliens, which are undetectable by any means. Sometimes, or rather, rarely, two opposite factions of these find themselves in the same host and start a war. They probably utilize little versions of weapons of mass destruction on each other and the body spontaneously combusts. Or, or, it could be that the soul just shakes its head at the body and says: " AAym sick n tired of yoar stuffin yoself like a turkey at christmas with those there cakes un sweets, an tha lizard you ate was deees-gus-ting! Lets see how you fend foe yoself, without me!!" and then it ups and leaves. So the body, like a balloon without air, rapidly implodes, and from that pressure on the basic materials of every cell, the cells spontaneously explode, thus causing a singularly severe incendiary event, often called spontaneous combustion.
Anyhoo, these are only postulates of a hypothesizing mind, limited, as every single person is, by the constraint of only a single point of view on a matter, said matter philosophized upon without consultation of ones peers and without a healthy respect, or even an unhealthy respect, of the boundaries of commonly accepted logic.
Have a good day!!