Is intentional eating fast food to have health problems a sin?
Let’s do a situational approach:
Case A: Thomas works from sunrise to sunset. Throughout the day, he eats very unhealthily. He consumes coffee, plus added sugar and milk, on a daily basis. His diet is high on saturated fats and trans fats and empty calories due to consuming a lot of candy bars, soda pops, and cheeseburgers. His office job does not allow him to exercise or travel much. But because of his high-calorie, low-nutrient, low-fiber diet and low-exercise lifestyle, Thomas probably has high risks for high blood pressure and cardiovascular disease and other health problems.
Case B: David has suicidal thoughts. He wants to commit suicide but is too chicken to do it. So, he intentionally decides to eat himself to death by feasting on fast food, hoping that one day he would die of heart attack and stroke and not let anyone know that the true reason is to commit suicide.
Both seem to be intentional. Case B is more like planning your own death in an unique way. Case A is intentional but the individual feels trapped in his own situation.