User blog comment:Miskos3/Fairy Tail 514: Dragon Seed, Review/@comment-4449950-20161212114307/@comment-2214433-20161212115528

Well, I did try to read up on the whole body heat thingy and while in many cases it seems to be regarded as the last option to warm a person up, since it may also do more harm than good, it should also be noted that you don't want a random heat either... Say, if Evergreen made a bonfire next to Natsu, that'd actually screw him up more. So, at least Mashima's not completely talking out of his ass and using a real life procedure, but again, I'm totally sure he kept the fanservice in mind when drawing these panels.