I'd be curious about the sides and energy levels. I have a mate who is mid 50s and a good 50kg heavier than he should be. He's a big bloke over 6 ft so 50kg at that height is obviously different than if he were 5'7 or something, for perspective. He works as a tradie (building houses) and despite his size, keeps pace with blokes half his age - he also works longer hours than most. Whilst he doesnt exercise per se hes very active. His downfall is lack of time to do much at all outside of work, but he does like the odd few beers after knock off each day and obviously eats a lot more than he should.
SO he'd unlikely be able to find time to expend more calories, nor would he need to if his appetite were more under control, but I suspect he'd still hit the drink regularly. any idea how the two might interact, and secondarily - given his active work life and the necessity to keep up said pace, what will it likely do to his ability to work long hours of moderate-hard physical labour?
Asking for a friend?

The most severe and disgusting side effect for me is the stomach gas. Since GLP-1 slows down the passage of food through the digestive system any food that is already there will stay for much, much longer. I had already eaten a large chicken breast with some vegetables and hummus before taking the first shot... The next morning (10 hours later) I had severe burping and I could still taste the chicken, it felt like very little of it was digested.
At its worst when digestion is very slow stomach gas will build up and the burps will get stronger and have a very unpleasant, rotten eggs taste to them. The smell is terrible too, like farting from the mouth. The first time this happened I was burping for about an hour and not getting better and it felt like I had a rock in my stomach. Eventually the pressure got so bad I projectile vomited and just about made it to the bathroom (nice). I immediately felt better.
Needless to say after something like that, the food noise all but disappears and food in general becomes a disgusting concept. So for the first couple of months I could eat very small quantities. I think I've had one such episode in the last two or three months so it goes away. You just can't eat much, you'll pay for it. After a while you don't want to, many times a light meal left me feeling like I had just been to McDonalds.
Other sides is the diarrhea which follows such a throw up and it is nasty in a special way... I won't go into details. Once I had a severe stomach pain in the early hours that was so bad I felt like calling an ambulance. Like somebody was tearing me up inside.
Anyway, the pounds started coming off without any particular effort, just eating small amounts, usually protein, so I was free to focus on my job.
I know someone else who took semaglutide and they had none of the above, but their hair starting falling out at a much higher rate. This seems to be reversible after stopping.
Regarding energy levels they were ok, obviously lower since less calories are taken in. Not as bad as a PSMF with protein that was my standard diet. What I noticed immediately was:
1. The mood swings I used to get disappeared and crankiness was generally absent
2. It felt like somehow my blood sugar was not falling at too low levels, so the above was a side effect of that.
3. My sleep was not disrupted at all, as it would have been the case dieting without semaglutide.
I am sedentary, so not sure how it would affect someone as active as a builder. I imagine a priority for your friend is to be able to keep up with the young 'uns. I can't help much with that. If he wants to try it I would recommend taking it right before a bank holiday weekend, that way he can assess symptoms without having to find out on the job.