By the time we're in our 30s, most of us have already reached our peak in terms of lean muscle mass. From that point on, most of us are gradually losing muscle. It’s not obvious at first, but by the time you’re in your 60s or 70s, the difference in body composition is really dramatic. At that age, you usually see a lot less firm muscle tone and a lot more soft flesh and loose skin.
But age-related muscle loss isn’t just a cosmetic issue. So much of the loss of function and vitality that commonly accompanies aging actually begins with this gradual loss of muscle tissue starting in mid-life. As we lose muscle, we lose strength and stamina and this means we can’t do as much as we used to. We aren’t as strong and we tire more easily.
As you lose muscle, you also tend to lose bone tissue. Thinning bones eventually lead to the frailty, falls, and fractures that we typically associate with people in their 80s—but the seeds for this are sown way back in middle life when we start losing muscle mass.