This
is a drawback, but I'm not sure how terrible it is.
If you go off the drug, you regain your weight. If you go off your diet, you also regain the weight. That, then, is a wash.
These drugs currently cost a fortune, so lifelong dependence is an expensive scenario, especially since most insurances refuse to cover them. On the other hand, this is preventative medicine, which might significantly reduce costs from obesity-related health issues down the road, including heart disease, cancer, and arthritis.
Compliance with a weekly injection is also likely to be higher than compliance with a long-term dietary change. Of course, since something like 95-plus percent of diets fail long-term, almost anything would have a higher compliance.
I don't know that we have enough data on long-term use of these drugs to be confident about long-term side effects, either.
I don't love the idea of being dependent on a medicine for the rest of my life, but there are plenty of other lifelong medicines that we just sort of accept as normal now. Insulin-dependent diabetics and people with high blood pressure are just two examples.
I guess for now I'm putting these in my "cautiously optimistic" bucket.