India, July 9 -- When a patient asks a doctor which GLP-1 to start, the conversation usually turns on one number: how much weight will come off. It is the number the prescription is chosen by, the number the patient tracks, the number that decides whether the drug is judged to be working.

The most comprehensive comparison of obesity drugs to date complicates that approach. Published in The BMJ on Thursday, the analysis drawing on 262 trials covering nearly 100,000 patients has, for the first time, ranked GLP-1 weight-loss drugs not just on kilos lost, but on survival, heart risk, kidney health and quality of life.

The findings suggest the drug that sheds the most weight is not the one with the strongest evidence of protecting the heart,...