The Shocking Connection Between Muscle and Longevity - Healthy Living Association

The Shocking Connection Between Muscle and Longevity

As we grow old, our bodies change. While teens get taller and more muscular with age, adults start gaining weight, losing muscle and getting tired often. Aging is a natural process, but you can improve your quality of life. Luckily, researchers recently discovered new facts that could make retirement years healthier. The secret? Changing your body composition. Here’s what you should know.

What is body composition?

The human body has different types of tissue. Body composition is the specific distribution of total body mass among lean body mass, skeleton mass and adipose tissue. Some experts only use lean body mass and fat percentage to determine composition.

To figure out someone’s body composition, there are different methods available in-office or elsewhere. For example, DXA scans and biometrical impedance methods are usually available at cross fit gyms, while hydrostatic weighing and skinfold measures need to be performed by a trained medical professional.

How body composition changes with age

Researchers know our bodies change with every year that passes. In fact, body composition can be vastly different from one decade to the next, even if there is no weight gain [1]. According to epidemiological surveys, the typical us adult gains between 1 and 2 pounds of fat per year as the body’s metabolism gets slower. Unfortunately, this fat gain doesn’t tend to show in BMI calculations or overall body weight.

Risks associated with high-fat, low-muscle percentages

Humans need their body composition to be balanced to guarantee proper health. Too low body fat percentage can be as dangerous as too high. The CDC dictated body mass index is an adequate indicator of the effect of weight on your health.

BMI gives you a numerical rating based on height and weight. According to the CDC, healthy individuals will have a BMI index between 18.6 and 24.9. anything higher or lower than that could present health risks.

However, researchers have found that a higher body fat percentage, regardless of a normal BMI, can be equally dangerous to your health [2].

The American Council of Exercise recommends women strive for a fat percentage between 25% and 31%, while men should be between 18% and 24%. Athletic people can go as low as 14% for women and 6% for men. Anything less than that will keep your body from working properly.

Nowadays, the majority of the population deals with high body fat percentage, and turns out this can affect quality of life as years go on.

In fact, a recent study found that a low muscle percentage could make functional movements difficult. It could also increase the risk of conditions like stroke, osteoarthritis, kidney disease and cognitive decline [3]. On the other hand, researchers found muscle mass loss, regardless of BMI, seems linked to a higher mortality risk overall [4].

Of course, not all adipose tissue is created equal. Here’s what you should know.

The biology of fat

The physiology of adipose tissue, also known as fat, is complex. In fact, researchers are currently still trying to understand how it functions and how it affects our quality of life.

What we do know is that not all adipose tissue is the same, and their location and type might be more important than overall body fat percentage [4]. Considering older adults change body composition even while staying at a healthy BMI, this is especially vital to preserve quality of life.

For starters, adipose cells are essential to many physiological processes. In fact, subcutaneous adipose tissue -or the fat under the skin- could improve cardiovascular health [3]. But when adipose tissue is stored outside of subcutaneous locations -like the liver and the abdominal region- it can be dangerous. This type of fat storage has been linked to chronic inflammation, liver failure, increased cholesterol and decreased strength. Unfortunately, older adults are particularly at risk.

Why extra fat can be dangerous

The problem with fat is that it is considered a functional tissue. Contrary to what one might think, fat serves a purpose just as muscles and bones. In fact, adipose tissue processes and releases many hormones. This is the reason women need a certain percentage of body fat to have a menstrual cycle.

When fat is stored outside of subcutaneous reserves, it starts producing different chemical compounds that can damage our health. Then, a high body fat percentage leads to a general inflammatory state while sending excessive endocrine signals. In turn, these hormones affect how other essential systems work, including the heart and the central nervous system. Non-subcutaneous fat also releases hormones that increase insulin resistance and your chances of becoming diabetic.

Since most overweight people store fat in their abdomen, waist measurements can be linked to higher mortality risks. But the study done at the University of Pittsburgh specifically showed that adipose tissue located within the muscles seemed to be as dangerous for long-term health as visceral fat in the abdomen.

Intermuscular fat in older adults

A study from the University of Pittsburgh found that higher intermuscular fat -also called intermuscular adipose tissue- increased mortality risk [4]. On the other hand, higher rates of lean muscle mass seemed to protect against mortality among people of normal weight. Unfortunately, the older the patient, the faster they lost lean muscle mass and seemed to accumulate more intermuscular adipose tissue.

In this study, researchers found older adults showed a redistribution of fat storage. This happened even if adults retained the same weight or lost weight. As such, subcutaneous fat deposits shifted towards ectopic locations, including visceral and intermuscular fat storage [4]. In such cases, BMI index wasn’t enough to estimate health risks since this dangerous fat deposits aren’t counted in that equation.

Intermuscular fat (IMAT) plays a role beyond increasing mortality risk. In fact, researchers recently found IMAT had a big impact in muscle function loss in older people. To figure this out, they measured muscle loss and compared it to muscle function over several years. Function was measured using grip strength and general fitness tests.

The results were astounding: muscle function was significantly lower than expected in relation to actual muscle loss. Older adults with higher IMAT in the legs showed lower muscle strength and function. This means intermuscular fat keeps muscles from working properly, which in turn increases your risk of injury and worsens quality of life.

The impact of low muscle mass and high IMAT in the muscles is so serious that the European working group on sarcopenia in older people recently suggested to change the medical definition of sarcopenia. Currently, sarcopenia is “the gradual loss of muscle mass that can affect people in their 30s and beyond”. However, experts in the group suggest the definition should also include loss of muscle function, since this is what mostly affects quality of life and functional movement among older adults [5].

How to live longer by increasing muscle mass

Taking into account lower muscle mass and high intermuscular fat are related to higher mortality risk, if you’d like to live longer controlling those two variables is key. So what can you do to prevent this natural process? In general, you should follow the same recommendations given to prevent and lower transverse abdominal fat:

  • Do 30 minutes of moderate exercise every day: cardiovascular activity helps you lose overall fat. Plus, it will improve your cardiovascular health.
  • Include weight training into your routine: this is the best way to preserve and increase your lean muscle mass percentage. Aim for at least 2 sessions a week on non-consecutive days.
  • Make sure you’re eating enough calcium: calcium could help control ectopic fat storage, which is the type you should prevent. Try to get calcium from natural sources like greens and dairy instead of supplements.
  • Sleep enough: chronic lack of sleep increases your cortisol levels. In turn, this hormone makes your body store visceral and intramuscular fat.

Final thoughts

As you can see, increasing lean muscle mass is possible for older adults. Luckily, official recommendations are very easy to follow. Plus, they’re similar to what most people understand as a healthy lifestyle. Living for longer is possible with the right changes!


  1. St-Onge, M. P., & Gallagher, D. (2010). Body composition changes with aging: the cause or the result of alterations in metabolic rate and macronutrient oxidation? Nutrition (Burbank, Los Angeles County, Calif.), 26(2), 152–155.
  2. Gallagher, D., Heymsfield, S. B., Heo, M., Jebb, S. A., Murgatroyd, P. R., & Sakamoto, Y. (2000). Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. The American journal of clinical nutrition, 72(3), 694-701.
  3. Addison, O., Marcus, R. L., LaStayo, P. C., & Ryan, A. S. (2014). Intermuscular fat: a review of the consequences and causes. International journal of endocrinology, 2014. Available here.
  4. Santanasto, A. J., Goodpaster, B. H., Kritchevsky, S. B., Miljkovic, I., Satterfield, S., Schwartz, A. V., Cummings, S. R., Boudreau, R. M., Harris, T. B., & Newman, A. B. (2017). Body Composition Remodeling and Mortality: The Health Aging and Body Composition Study. The journals of gerontology. Series A, Biological sciences and medical sciences, 72(4), 513–519. Available here.
  5. Marcus, R. L., Addison, O., Dibble, L. E., Foreman, K. B., Morrell, G., & LaStayo, P. (2012). Intramuscular adipose tissue, sarcopenia, and mobility function in older individuals. Journal of aging research, 2012. Available here.

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