1 there are many things that can cause slimmers to backslide:
relapse, lapse, regress, retrogress, revert to one's bad habits, weaken, lose one's resolve, give in to temptation, go astray, leave the straight and narrow, go down the primrose path.
▷antonyms persevere.
2 his only worry was that if she left things would backslide:
degenerate, deteriorate, slip, slide, fall off, revert to a former state, regress, retrogress;
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