Why A Lack Of Muscle Is Making You Fatter As You Age


Have you ever wondered why your body appears to be softer, with less perceived muscular definition than it once was?  Maybe you’ve even noticed an increased difficultly performing simple tasks of daily living, or worse, find yourself slowly losing your independence.  Hopefully things haven’t advanced far enough where you’re experiencing the latter.

Maybe you’ve just blamed it on hormones or just another inevitable consequence of getting older.

While it’s true that there are many biological changes that occur universally as people age, the main reason why people accumulate body fat and develop mobility issues stems from a rapid degeneration of the muscular system.

So what’s so great about having muscles anyway? 

Muscle serves the body in many ways.  Some of its most important functions include:

  1. the generation of heat (thermogenesis);
  2. the utilization of stored body fat and glycogen as fuel;
  3. stability of body position and posture;
  4. regulation of organ function;
  5. the elimination of waste;
  6. the circulation of blood;
  7. production of amino acids required for immune cell replication; and
  8. the ability to move in sport, recreation and athletic activities.

As most people age, they tend to lose nerve and muscle connections, which greatly decreases their ability to use their muscles.  Muscle size will also be reduced, resulting in significant tissue loss over time.  Muscle and lean tissue loss (bone mass, ligaments, cartilage, connective tissue) associated with aging is a phenomenon called sarcopenia (derived from the Greek words for “vanishing flesh”).  Sarcopenia disrupts the natural function of the muscular system, impeding many of the important muscle functions I’ve listed here.

In fact, as much as 35-50 percent of an individual’s muscle mass can disappear between the ages of 20 and 90.

By age seventy, some muscles may have lost as many as 50% of their motor units and 75% of their muscle fiber numbers.  Loss of muscle in seniors is due primarily to this decrease in the number of muscle fibers and significant atrophy of type II muscle fibers ( the ones that produce the most force).

As it relates to body composition (the intent of this article), less muscle means less heat, less fat burning potential and problems with fatigue, immune weakness and a high susceptibility to injury.  By age 30, adults will experience a gradual decrease in muscle density (about 10 ounces/year) and increased intramuscular fat ( about 1 pound/year).

In healthy young people, 30% of total bodyweight is muscle, 20% fat and 10% bone.  By age 75, about 15% of total bodyweight is muscle, 40% fat and 8% bone.  Thus, half the muscle has vanished due to sarcopenia and is subsequently replaced with twice the amount of fat.

muscle loss with age
Notice how fat levels increase by 45 lbs and %fat doubles by age 50!!!

Not a pretty picture is it?

So what causes Sarcopenia and how can you prevent it? 

Sarcopenia is not completely understood or properly defined.  It is thought to occur as a  result of several internal systems (hormonal, nervous, muscular, cadiovascular etc.) slowing down with age.

External forces also contribute.  One theory suggests that sarcopenia is the result of exposure to the earth’s natural forces, which cause the breakdown and decay of everything on the planet over time through oxidation.   Oxidation is the natural degradation of high energy molecules to low-energy molecules and occurs as a result of continuous exposure to oxygen, radiation and light.  These forces tend to erode and waste everything they come into contact with, including  you and me.  It’s the ultimate paradox; that which gives us life (oxygen) ends up killing us in the end.

Research is beginning to show that inadequate intake of certain nutrients, namely protein, can cause muscle loss and suppressed immune response as well.  Many older adults (about one in three), especially women, are eating less protein than they should and are likely experiencing some form of impairment of its utilization. The current minimum recommended intake of 0.36g/lb of body weight should be used as a minimum standard to prevent depletion of lean tissue in the body.

Our lifestyle choices have perhaps an even greater effect on sarcopenia.  Most notably, due to sedentary living, a progressive loss of connections between nerves and the muscle cells they control occurs, making it more difficult for the nervous system to stimulate muscle cells.  As our society progresses (or regresses) to a more sedentary and automated way of life, the burden of sarcopenia becomes even more prevalent.

The good news is that sarcopenia need not be thought of as an imminent consequence of aging but rather an imminent consequence of disuse.  This is something you can control.  You may be at the mercy of the Earth’s natural forces, but you can still get off your butt and do something to slow down their effects.  There is only one natural remedy to greatly impact how much muscle you lose and how soon you lose it.  Of course, I’m talking about exercise.

Regardless of your age or condition, almost everyone can safely improve their health and independence though exercise and physical activity.  Even better, get yourself on a weight training program. Recent studies have shown that as little as ten weeks of resistance training can add 1.4 kg of lean body weight, increase resting metabolic rate by 7%, and reduce fat weight by 1.8 kg.

So go learn to lift weights with a qualified strength trainer have a delicious protein smoothie and start building some muscle – because muscle is a terrible thing to waste!

Craig Simms

Craig Simms

Craig Simms is a personal trainer and weight loss coach in Vancouver, B.C. Craig has been a fitness leader for over 21 years and has amassed over 25,000 hours of personal training experience in that span. He specializes in personalized weight management programs.
Craig Simms
Craig Simms

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