I'm 53, and 11 months out from a triple CABG (Coronary Artery Bypass Graft) surgery and humming along. This is me 9 months after open heart surgery.
I've a great example of how we can slow down the aging process, recover from trauma...doing all the right things. As my cardiac team says "You're not a typical cardiac patient." Nope. I'm not. By design.
2 weeks ago, I dropped by the cardiologist's office; his response, "Damn! Look at you!"
As we get older, our estrogen to testosterone ratio gets out of wack (we become more female), and it becomes harder to stay both lean, and to put on muscle. While I'll never do those 12 plates on each side of the leg press ago, my prognosis is very good, and my health care team encouraged me to compete at a high level again this year. We'll see. I'm still having some trouble breathing, but, I have milestones, ever few weeks.
Statin use held me back, and I'm not on statins any more because they do more harm than good in most cases, destroying muscle, and running your CK off the chart, eventually leading to muscle injury. My cholesterol was never over 138. (I was on statins only for a few months, and my CK went off the chart and I had two grade 2 muscle tears, so, no more statins. They wreck muscle, and recovery.)
I'd look at adjusting your testosterone levels up. Any informed doctor should be willing to help you do so. If they don't, they either don't know what's up or you have some other risk factor. The benefits of that therapy in mood, skeletal muscle, brain health, disease prevention, are all compelling reasons to go down that path. (FYI, my PSA is a 0.04, after years of bodybuilding, and we know now that PSA is not a reliable indicator of prostate cancer, and the prostate cancer is not from high test, but, rather, the test/est ratio being out of wack...age.)
I've spent hours talking with doctors who work with folks of age, and with HIV, and all the risks and benefits. I'd go down that path, without hesitation.
As my team puts it "We'd rather see you in great shape, doing what you love, than home depressed and dying."
And, to toot my horn a bit more....11 months out from being sawed in 1/2, I can take my heart rate to 110% of max (for bursts) on a good day.
View your body as a machine. Treat medical folks with skepticism (many have dated education; use the same silly protocol for everyone), and do your own research.
For being not "skinny fat", keep your calories up, build muscle.
Resistance training is the ONLY WAY, other than T3/T4 to raise your metabolism AS YOU GROW OLDER, but, if you don't eat enough, your body well consume your muscles to save you from the famine. Preferred sources: carbs, protein, fat. While it's true that lower blood sugar level will cause some fat conversion, what is more effective is HIIT interval training (which also does amazing things for your cardiac health), and resistance training to encourage higher BMR (Base Metabolic Rate). HIIT can raise your BMR off the chart, but...you have to be able to do it, and ease into it. It's hard. It's draining.