As Wilum says, there are any number of myths about HPL, and any number of stories which are of this nature, some few of which are true (at least partially), while most are not. As for the bit about de Camp mentioning the stories about Lovecraft tearing off the WT covers... yes, he mentions it, only to debunk it, if memory serves. At any rate, Lovecraft's collection of issues of Weird Tales can be consulted at the John Hay Library, and they are intact, so....
Brian, it was also de Camp who put a label on this "illness" he was supposed to have which made it difficult for him to regulate his body temperature, using the term "poikilothermism", which is simply a descriptive label for animals (such as reptiles) which have this quality; it isn't an actual disease. Joshi has posited the most likely explanation by tracking down a fall Lovecraft had when young, from quite a height apparently, causing a severe injury to his head. This may have in turn damaged that portion of the brain which regulates body temperature, something which is likely to grow worse with age... which his condition certainly did (he could -- barely -- tolerate extreme cold when younger, but by his later years even a dip into the thirties or twenties could render him unconscious and cause problems with his breathing as well as causing severe edema). There are other factors which may have been involved, as well....
He did have a passion for sweets, though I don't recall him sprinkling sugar on jam... he did, however, use copious amounts of sugar in his coffee, so much so that a sludge was left at the bottom of the cup. His health problems, however, may not have been so much organic as tied to his nervous system, particularly the fact that he had nervous disabilities which caused him a great deal of trouble at various points. Much of this, interestingly, calmed down quite a bit following the death of his mother, when he began to emerge from the hothouse atmosphere of their joint residence on Angell Street. It never went away, but (sad to say) her death may well have allowed him to live the much healthier life he did in the ensuing years, when he was anything but an "eccentric recluse", traveling quite extensively up and down the eastern seaboard, from Quebec to Saint Augustine, Florida. The interesting thing about this is that, despite the fact that he himself largely shared the image of himself as a reclusive individual, he seemed to make friends wherever he went, no matter what their socioeconomic status or "class", and the numerous accounts by people who met him are almost glowing with accounts of his goodfellowship and kindness toward others -- quite a contrast to the curmudgeonly caricature so often depicted.
