My impression from watching various people debating studies on the topic, is that even more important than protein is physical activity, when it comes to stopping muscle loss. Someone sitting in a box eating nothing for a month will come away from it with all sorts of health issues compared to someone who walks for half an hour and otherwise lives normally, despite the second person supposedly having higher energy and nutritional needs. Physical activity is a powerful signal to the body to maintain itself. This is why the health of bedridden people looks like a horrible feedback loop that destroys them.

Another issue that makes me wary is that normally when fasting, there’s an initial period of being hungry, followed by adaption and minimal/no hunger. After a few weeks (or longer if there are special circumstances), hunger should eventually return, and this is your signal to start eating again regardless of plans. What concerns me is that Ozempic may prevent the return of hunger signal. I could see this leading to malnutrition, which another post already mentioned in a different way.

In the UK those products are only available to people with a BMI > 30. If you have 20 or 30 kg to lose it is simply not true that most of the weight loss is muscle mass. The fat is visible and the fat loss is also visible. You might lose a bit of muscle mass, and doing exercise at the same time is good. But between the loss of a bit of muscle mass during the diet vs remaining obese, it is an easy trade off from a health point of view.

BMI is an empty metric anyway, you can be VERY muscular, slim but not very tall and still being in the same category of a near obese person.

Great, so professional bobybuilders who are no fat all muscles shouldn't start a diet on ozempic...

It's a bad metric both ways, one can be really skinny with almost no muscle and all fat, and still be in a "healthy" BMI range.