Obesity and asthma occur together often, each makes the other worse, and losing weight improves asthma outcomes. That is the stated reason this review was conducted, and the exacerbation evidence on the efficacy side is in a ratio of 0.438, a difference of 2.2 points. The safety question is separate: do these drugs themselves cause breathing problems[1].
The answer is no, as far as the data goes. Across 123 studies, liraglutide, semaglutide, tirzepatide and naltrexone-bupropion were not associated with increased respiratory adverse events compared with placebo, and the randomized trials contributing carried a low risk of bias. For a class taken by tens of millions of people, that is a useful null.
What counts as a respiratory adverse event in a weight-loss trial is worth knowing too. These are dominated by upper respiratory tract infections, which is to say colds. A null result on that measure says these drugs do not make people catch more colds. It is a weaker statement than “these drugs do not affect the lungs”, and the two will be reported as the same thing.
Three drugs could not be assessed at all. Insufficient data limited comparisons for orlistat, phentermine-topiramate and setmelanotide, which means they are unmeasured rather than cleared — a distinction that matters given phentermine-topiramate’s position in the network meta-analysis of nineteen drugs, where it ranked among both the more effective and the less tolerated.
For anyone with asthma weighing one of these drugs, the practical position is that nothing suggests harm and almost nothing has been measured in people like them. That is a common shape in this literature, and it recurs in the COPD flare-up comparisons and the analysis in older adults, where the population studied and the population asking are not the same people.