Jiǎnféi jìhuà shīshǒu, tā yòu kāishǐ bàoyǐn bàoshí.
His diet plan fell apart and he started binge-eating again.
Tips
usage
失守 is primarily a military term meaning to lose a defended position, but it is commonly used figuratively in modern Chinese to describe giving up on any plan or commitment — such as a diet or a rule one has set for oneself.