Brian Boyd wrote in Vladimir Nabokov: The American Years that Nabokov compulsively smoked Gauloises while writing but after visiting a physician due to heart palpitations Nabokov was advised to give up smoking. To ward off the nicotine cravings he started "...compulsively devouring molasses candy..." and subsequently gained sixty pounds.
Nabokov shared in a Playboy interview, "I became as stout as Cortez-- mainly because I quit smoking [while writing] and started to munch molasses candy instead, with the result that my weight went up from my usual 140 to a monumental and cheerful 200."
According to Secret Lives of GREAT AUTHORS Balzac often wrote for fifteen hours per day while drinking fifty cups of Turkish coffee. Unsurprisingly. it's suspected that the copious amounts of coffee contributed to his early death.
Compared to Balzac, I drink a meager five to seven half cups of coffee per day, often while writing, with one teaspoon of organic cane sugar; however, when I decided a month ago to forgo the sugar I subsequently lost a considerable amount of weight. I went down a shirt size and two belt loops!
Thus, be careful about what you snack on while writing.