The Surprising Connection Between Muscles and Longevity

Weight training

Throughout society, there is strong social pressure for people to lose weight and get healthy. Some of this pressure comes from the obesity crisis but a lot of it simply comes from the body types that people view as being attractive.

This obsession with appearance has many negative impacts, but one significant issue is that it makes us focus on fat, so much so that we forget about body composition as a whole.

Realistically, being fat or thin is only part of the equation when it comes to your body and your health. The other key part is your muscles. This means that we really have to pay attention to both the fat and the muscles in our bodies.

But, why are muscles important?

One relatively recent study (Srikanthan & Karlamangla, 2014) asked this exact question, in relation to muscle mass in older adults.

The key concept for this paper was the fact that fat and muscle have different impacts on our metabolisms. By extension, fat and muscle can also affect health in different ways. With their research, the authors aimed to understand how significant these differences were and their implications for how long people live.

The Study Itself

The research study made use of data from the National Health and Nutrition Examination Survey III. The authors specifically considered information from males who were 55 years or more and females that were 65 years or more, at the time of the survey. The authors also made some other exclusions, such as not including participants who were underweight or undernourished. In total, this resulted in a sample size of 3,659 participants.

The data was then analyzed using a range of statistical tests, with the authors looking for the relationship between muscle mass and death by any cause (all-cause mortality). In their analyses, the authors also accounted for a number of different factors that could confound results, such as race and gender.

One aspect of the analysis involved breaking down participants into four groups based on muscle mass and then comparing them.

The authors found that the overall rate of all-cause mortality was significantly higher among the group with the lowest level of muscle mass than it was in the group with the highest. The overall pattern can be seen in the image below:

Muscle mass and risk of death

In general, these outcomes indicate that the people in the lowest two groups of muscle mass had a higher overall risk of death than those with higher amounts of muscle.

The authors also noted that the patterns they observed could not be explained by factors like standard cardiovascular risk factors or issues with glucose regulation. As such, muscle mass was an independent factor predicting the risk of death.

Strengths and Limitations

The authors noted that this was one of the first studies to consider the relationship between muscle mass and mortality in such a large and representative population. Additionally, the study was significant because it considered muscle mass in an older population. As such, the size of this study and the population that it used were both significant advantages.

Another strength of the study was that the authors considered a range of possible confounding factors in their statistical analysis. This increases the chance that the observed relationships were actually present.

Despite these strengths, there was still one key limitation of the study, which was the fact that it was observational in nature.

Flexing arm

Observational research is always a bit tricky. On the one hand, it can be a powerful way to see patterns in a population and it often reveals patterns that wouldn’t have been evident otherwise.

After all, it would be practically impossible to look at longevity in an experimental study, because you couldn’t get people to follow the experimental approach for that long (an experiment like that would probably also be considered unethical).

But, at the same time, an observational study is limited because it cannot test cause and effect. As such, the authors cannot be entirely confident that the change in risk of death was caused by muscle mass.

Nevertheless, the authors do note that even if a cause and effect relationship is not present, muscle mass does still act as an important predictor of life length. This means that low muscle mass could potentially indicate other health problems, such as poor nutrition or insufficient exercise.

Likewise, regardless of cause and effect, the outcomes of the study support the idea that we need to start looking beyond body mass when considering health. Instead, we need to pay much closer attention to body composition and to muscle mass.

Why Are Muscles Important?

This is just a single research study, so it cannot completely answer the question, why are muscles important. Nevertheless, it offers important insight into the discussion of muscle mass and health. More than anything, the study reinforces the idea that fat and muscle differ in the impacts that they have on the body. As such, it is important for individuals to focus on both areas as they try to improve their health.

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Now, the study did just focus on older adults, but other researchers have found evidence of similar patterns in the population as a whole.

In fact, some researchers have even begun highlighting a related issue, known as normal weight obesity.

This essentially means that a person might be considered normal weight (or even skinny) but they have a relatively high proportion of fat compared to their muscle mass. The site Hack Your Fitness offers more information about what this means and how to overcome it. 

This body composition is actually at risk of a range of negative health outcomes, such as an increased risk of heart disease and diabetes (1,2,3).

A separate study also indicated that fat free mass had the opposite effect on mortality than fat (4), further reinforcing the idea that muscle mass can help increase longevity.

Additionally, the importance of building muscle is one reason why getting enough protein in your diet is absolutely essential for your overall health. Thankfully, there are many options for doing so, such as this list of high-protein recipes from Muscle & Strength.

Overall, the outcomes of this particular study agree with what other literature is saying, which is that we need to be placing a greater emphasis on muscle development.

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How about you? Do you focus on muscle or just on fat?​

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