If I am right about aging and that it results (in part) from mitochondrial inefficiency then it is obvious what the mechaisms of CR are that are relevant to aging
a) more mitophagy
b) lower peak glucose levels (less ROS, less mtDNA damage).
The question I think is really what happens with the mitochondrial DNA. With fission any DNA is replicated (although that is a complex issue). With fusion it is not clear that DNA is destroyed also it is not clear whether there is a selection process to destroy the worse mtDNA.
With mitophagy there is a process whereby the less efficient mitochondria are selected for destruction (ignoring the ATP Synthase issue).
I don’t think you produce less bile acids after gallbladder removal. The gallbladder mainly make sure most of the bile is released postprandially but without a gallbladder you still produce and release a lot of bile, it’s just released constantly throughout the day and night rather than the release being concentrated around meals.