The side-effects would need to be pretty extreme for the cost-benefit analysis to show using weight-loss drugs was more harmful than being obese.
I'm somewhat uncomfortable with the idea of muting some of our reward pathways in the brain though. Anecdotal reports so far have had people saying it has helped them with alcoholism and gambling in addition to losing weight, which makes me wonder if we're using a sledgehammer to crack a walnut. At the same time I don't have a genetic disposition towards gaining weight so maybe I'd have a different opinion if I'd tried everything else to lose weight and had felt out of options before these drugs came along.