Losing Muscle After 40

Most people expect to lose some strength as they age. Fewer realize how early it starts or how quietly it happens. Without resistance training, adults lose roughly 3 to 8% of their muscle mass per decade after about age 40, and the rate tends to speed up after 60. The medical term for age related loss of muscle and strength is sarcopenia.

Why muscle slips away

A few things happen at once. Activity usually drops in the 40s and 50s, and muscle that is not used is not kept. The nerves that drive muscle fibers thin out, so some fibers lose their connection. Hormones that support muscle decline. Muscle also becomes less responsive to protein, so the same meal produces a smaller building signal than it did at 25.

Strength tends to fall faster than size. That matters because strength and power are what keep you steady on stairs, quick to catch yourself when you trip, and able to get up off the floor.

Why the scale hides it

Muscle loss rarely shows up as weight loss. The space it leaves is usually filled by fat. A hypothetical 45 year old woman can weigh the same at 55 as she did at 45 and still have lost 6 pounds of muscle and gained 6 pounds of fat. Her weight looks stable. Her body composition has moved in the wrong direction on both counts.

That shift has consequences beyond strength. Muscle holds most of the body's stored glucose and is the main tissue that pulls sugar out of the blood when insulin rises, so less muscle makes blood sugar harder to control. Lower muscle in the arms and legs also predicts frailty, falls and fractures later in life.

It can be measured

A DEXA scan measures lean mass in each arm, each leg and the trunk. From the arm and leg numbers we calculate ALMI, the appendicular lean mass index, and compare it to people of your age and sex. That tells us whether you are holding muscle, losing it, or starting from a lower reserve than you thought.

Measuring it matters because the fix works best early. The two main levers are:

• Strength training, two to three days a week, with loads that get heavier over time. Muscle responds to this at any age.
• Protein, about 1 gram per pound of lean body mass per day, spread across 3 to 4 meals of 30 to 50 grams.

A repeat DEXA about every 6 months shows whether those changes are holding muscle where it should be.

That's why we check it.

Book a DEXA scan at HYBRD Health ($199)

This article is educational and is not medical advice.