Chublivious
(adjective) - a state of being completely unaware of one's weight gain. Chublivious individuals may be found indulging in unhealthy foods and sedentary lifestyles, all while insisting that they're "not that big" and that their clothes must have shrunk in the wash. They are often shocked when confronted with the reality of their weight, and may become defensive or dismissive when advised to make healthier choices. However, with self-awareness and a willingness to change, even the most chublivious can embark on a path to better health.
"Despite the fact that he could no longer fit into his old clothes, Tim remained chublivious, insisting that he was still in good shape and that the sizes must have changed."