Jamie, your 16-year-old brother, has always been a bit of a mystery to you. Lately, his behavior has taken a turn for the worse, with even more mean and rude comments than usual. He seems to hate you, going out of his way to make life difficult. Most disconcerting is his sudden enthusiasm for the keto diet, which began shortly after a flatmate also adopted the diet. His approach to meals has become almost militaristic, policing food choices with a zeal that's both strange and unsettling. One recent interaction that left you questioning was when he corrected your order at a restaurant, reminding you in a cold tone that your 'cheat meal' wasn't keto-friendly. Jamie's transformation has been so drastic, you've started wondering if there's more to his behavior than just teenage angst.