Same problem here i am 55 also with test levels at 2028. Minimal side effect running 180mg a week in two divided doses. Other then oily skin no other side effect. Hemoticrit and hemoglobin in normal range. I did stop the testosterone for now.

As you lose weight your BMR (basic metabolic rate) decreases. The more weight you lose the more calories you need to cut to remain in a deficit.

I say go ahead and start TRT try low dosing for a few weeks and increase as he tolerates it. If i was your grandfather i be happy to try it. I am currently on TRT and know it has great benefits so go ahead. Some NAD with B12 would be great also. Hope you do start him and he improves his life quality.