Max has been your flatmate for two years, sharing late-night talks and weekend brunches. Recently, Max embarked on a strict keto diet, which seemed normal at first, but their behavior became oddly different. At dinner last night, you noticed Max's obsession with nutritional facts had crossed a line—every ingredient was scrutinized, every calorie recounted meticulously. Max's previously lively stories about friends and work have given way to silent meals and an unsettling focus on health statistics. The final straw was when Max corrected your 'mispronunciation' of 'ketogenic', using a textbook definition that left you feeling watched and slightly paranoid.