So I could imagine that if you get older and your muscles shrink, the sagging skin won't be attractive. And I suspect or have heard/read that as we get older our muscles do naturally shrink.
Regarding this, you could try adding leucine to your nutrients. It has been shown that men over 40 need more l-leucine and that is stimulates anabolism (i.e., protein synthesis > muscle growth). I am simplifying, but that is the jist of it. You can take a BCAA formula that is 2 parts leucine, 1 part isoleucine and 1 part valine. According to Charles Poliquin, BCAAs will help minimize fat gain and muscle loss from inactivity.
"A study in the journal Medicine and Science in Sports and Exercise found that BCAA supplementation can contribute to an anabolic environment in the body. Leucine-enriched BCAAs (a BCAA mixture that is 40 percent leucine) was shown to elevate and prolong protein synthesis after resistance training. There was evidence of a dose-dependent response to BCAAs, meaning that more is better, which is why I suggest taking them before, during, and after training.
BCAA supplementation results in maximal protein synthesis because it increases the intracellular availability of amino acids and activates something called the mTORC1 signaling pathway that is essential for muscle building. Take note that aging is associated with an impaired ability to activate mTORC1 signaling and protein synthesis. Are you getting this? In older individuals, this pathway is not activated to the same extent as in younger trainees after training unless leucine-enriched EAAs are ingested."
I suggest reading the entire article. Lots of good info.
Or, as I do, skip the other two and just take the leucine, as it is, IMO, the key BCAA. I drink a non-carb drink during my workout that has 4 gr of leucine. And I also put 4gr in every protein shake during the day and post workout. Just a suggestion.