With aging, your strength and stamina begin to decline from hormonal changes and natural wear-and-tear on the body. Provided you are working within your personal strength and recovery limits, your training doesn’t need to change from when you’re young. You may not be able to lift as much or for as long, but you can still push yourself and provide a healthy growth stimulus. As for diet, that doesn’t change at all. Eating a healthy diet rich in protein is important regardless of age. Arguably, the one thing you can do to make the most difference is hormone replacement therapy (HRT). If you opt for this, you definitely want regular labs done to ensure your hormones are in a healthy range. Menopause for women isn’t natural, it was simply evolution’s way of having you start to allocate resources towards the young rather than reproduction. For men, there is no evolutionary basis for the decline in testosterone. Using creams that let you have better control over the rise and fall in hormone concentrations that occur naturally is ideal, since you can apply and wash off the creams to match the hormone’s circadian rhythm. That may minimize the risk of any side effects. The book Estrogen Matters is excellent to learn about HRT for women: https://amzn.to/2TEl68V
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