glp1 doesn't increase your basal metabolic rate, it curbs your appetite. so it's still possible to ingest an excess of energy and to maintain your energy storage volume if you continue the dietary habits that got you fat in the first place -- eating slop and/or eating for the sake of eating.

even one caffeinated corn syrup slurpee that people consume like it's no big deal can be a quarter or more of your daily energy requirement. a few snacks on top of that and that leaves preciously little budget for real food.