It's inflammation but, from the sugar/carbs, up your healthy fats especially omega3s, cut out all sugar/processed foods and watch that pain subside.
Tesla never complained about bread & he was very skinny ........................ .....
i dont get any workout benefis from fat ..backstory... when i was eating beans and rice i also experimented with fats from pb and cashews, neither one boosted my workouts... ive already been down that road bro... but i didnt have any back pain then eating like that but i had no spark in my workoutsi eat an avacado perday though but no gainz from it