Changes in Female Body Composition with Age

Why Does My Metabolism Seem to be Slowing Down?

As we get older our muscle mass reduces with inactivity.  Given that muscle is a highly active tissue that burns a lot of energy, a reduction often leads to weight gain.  This makes resistance training imperative to curb the decline and possibly restore muscle mass/tone. 

The age old adage still applies - If you don't use it, you’ll lose it!

How Much Muscle Am I Loosing?

That all depends how old you are.  A 65 kg Female will have approximately 18 Kilograms, or 28% of muscle at the age of 30¹.  For every 10 years of inactivity your muscles will decline by 1.1 kg or 6%³!  So that means if you don’t do any significant resistance training between the ages of 25 and 55 years old you will loose approximately 3.3 kg or 18% of your lean muscle! 

How Much Fat Does My Muscle Burn?

Your fat free mass burns approximately 22 calories of fat each day², per kilogram.

That’s 660 calories per month!

Lets go back to the original example.  If you are 55 years old and have lost 5.7 kg of muscle;

· This means that your metabolism has slowed down by 3762 calories per month!

· The average person that runs a marathon (5 minutes per km) uses approximately 2000 calories.  You would almost need to run 2 marathons a month to burn the same amount of energy  as when you were 25!

Reference

1. Appendicular skeletal muscle mass: effects of age, gender, and ethnicity

2. Can Diet and Exercise Really Change Metabolism

3. Skeletal Muscle mass and distribution in 468 men and women