> So has anyone managed to separate the effects of semaglutide from the effects of weight loss?

I was looking for that in particular. The study does say:

"To assess whether the observed effect was mediated by weight reduction, we performed a sensitivity analysis adjusting for change in BMI from baseline to week 104. In this adjusted model, the treatment effect coefficient was attenuated from β −0.092 to β −0.066 (P < 0.001), corresponding to a reduction of 28% in the estimated effect size. This attenuation indicates that 72% of the treatment-associated difference in 20-year dementia risk persisted after accounting for BMI change, suggesting that mechanisms beyond weight loss contribute to the observed proteomic signature modification."