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Could working out - and specifically building muscle - lengthen your life span? A new study indicates that it could, and that muscle mass may be a better indicator of overall health than BMI.

Do you think building strength and muscles is for the young? Think again. New research shows that older adults can extend their life by working out regularly and building stronger muscles — and your life expectancy increases in direct proportion with your muscle mass. 

What does the study tell us about the importance of strength training throughout life, and about the way in which health is currently measured?

Lift Weights And Extend Your Life?

The research team, led by Dr Preethi Srikanthan, was published in the American Journal of Medicine. Dr Srikanthan — an assistant clinical professor in the endocrinology division at the David Geffen School of Medicine at UCLA — and his team used data from the National Health and Nutrition Examination Survey (NHANES) III. This long-term survey ran from 1988 to 1994, but the research team zoomed in on older adults. 

The 3,659 they focused on were 55 or older (men) or 65 or older (women) when the study was ongoing. Using a follow-up report from 2004, the team then determined which of those individuals died from natural causes. They found that body composition played an important role. 

How did the team go about determining body composition? Body Mass Index or BMI might be the first thing that comes to mind, but the researchers actually used "bioelectrical impedance" to look at the study subjects' body composition. This technique runs an electrical current through the body. That sounds scary, but isn't dangerous. It is done because the current passes more easily through muscle than through fat, giving researchers an insight into the muscle mass of an individual. 

Muscle mass is determined in a way similar to BMI, by looking at the overall muscle mass relative to a person's height. Older adults with the highest muscle mass were significantly less likely to die of any cause than those with the lowest muscle mass, the research team discovered. 

Muscle Mass Vs BMI

Co-author Dr Arun Karlamangla, who is an associate professor in the geriatrics division at the Geffen School, explained: "In other words, the greater your muscle mass, the lower your risk of death. Thus, rather than worrying about weight or body mass index, we should be trying to maximize and maintain muscle mass."

The "obesity epidemic" is a much talked-about problem, especially in the United States but also in other countries. Yet, calculating a person's BMI doesn't give a very good insight into a person's body composition. BMI is calculated by looking at a person's weight relative to their height. The higher a person's weight relative to their height, the higher their BMI will be.

Though a higher BMI can indicate that a person has too much fat, that is not always the case. To demonstrate that BMI isn't always the best measure, just ask a formerly obese person who sought to lose weight through dieting and training intensively what happened to their weight. Replacing fat with muscle means the weight comes off far less rapidly, yet people who take this approach are going to be healthier. 

Dr Srikanthan points out that there is "no gold-standard measure of body composition". He adds that "several studies have addressed this question using different measurement techniques and have obtained different results".

"So many studies on the mortality impact of obesity focus on BMI. Our study indicates that clinicians need to be focusing on ways to improve body composition, rather than on BMI alone, when counseling older adults on preventative health behaviors, Dr Srikanthan says.

The study wasn't perfect of course — no study is. The NHANES III survey does't allow researchers to conclude that it was, in fact, the higher muscle mass that was responsible for the longer life span of those older people who were more muscly. Correlation still doesn't equal causation. But, Dr Srikanthan says, "we can say that muscle mass seems to be an important predictor of risk of death".

Is that enough reason to encourage older folks to work out more often? We think so. 

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