A March 2014 study from University of California, Los Angeles (UCLA) shows that the more muscle mass you have as you get older, the less likely you are to die prematurely. The new findings add to growing evidence that overall body composition and ratio of fat-to-muscle is a better predictor of all-cause mortality than body mass index (BMI) alone.

BMI simply measures height to weight ratio and can be misleading... total body mass includes fat and muscle which have different metabolic effects. This study was designed to test the hypothesis that greater muscle mass in older adults will be associated with lower mortality.

The study titled, "Muscle Mass Index as a Predictor of Longevity in Older-Adults," was published in the American Journal of Medicine. This new study expands on previous UCLA research led by Dr. Preethi Srikanthan, an assistant clinical professor in the endocrinology division at the David Geffen School of Medicine at UCLA. In previous studies, she found that building muscle mass is important for decreasing metabolic risks like obesity and diabetes.

Body Mass Index (BMI) Can Be Misleading

"As there is no gold-standard measure of body composition, several studies have addressed this question using different measurement techniques and have obtained different results," Srikanthan said. "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."

The body composition of the study subjects was measured using bioelectrical impedance, which involves running an electrical current through the body. Muscle allows the current to pass more easily than fat does, due to muscle's water content.

Using this method, the researchers were able to determine a muscle mass index—the amount of muscle relative to height—which is more accurate than the traditional body mass index. Then, they looked at how this muscle mass index was related to the risk of death and found that all-cause mortality was significantly lower in the fourth quartile of muscle mass index compared with the first quartile.

Build Muscle, Burn Fat

In “The Strength Program” chapter of The Athlete’s Way, I give simple tips for structuring a resistance strength training program that will increase muscle mass. Building muscle mass burns fat by increasing metabolism.

A study from 2005 compared people who did aerobic-only exercise with those who included strength training into their weekly routine. After eight weeks, the aerobics-only group had lost three pounds of fat and a half a pound of muscle. The group that combined aerobic and strength training had lost ten pounds of fat and gained two-pounds of calorie-burning muscle. Below are some benefits of strength training from The Athlete's Way.

The Benefits of Strength Training

• Increases Hormones and Neurochemicals that Make You Feel Great: The good stress (eustress) of lifting weights triggers the release of human growth hormone, lowers cortisol, and releases endorphins, adrenaline, dopamine, and endocannabinoids.
• Reduces Muscle Loss: After the age of thirty you will lose about a pound of muscle every year. A pound of muscle burns about thirty to fifty calories a day at rest.
• Increases Muscle Mass: In a study of people lifting weights for twenty-five minutes three times a week, there was an increase of up to three pounds of muscle mass over an eight-week period. Relatively little time invested lifting weights pays huge dividends.
• Prevents Metabolic Rate Reduction: Because lifting weights increases muscle mass, it prevents resting metabolic rate from dipping. The more muscle you have, the more energy your body uses to sustain itself. Calories are used for fuel, not turned into stored energy in the form of fat.
• Increases Metabolic Rate: A three-pound gain of muscle mass translates into an increased metabolic rate of 7 percent. When you create muscle you use more calories all day long, even when at rest.
• Increases Glucose Metabolism: Consistent resistance weight training can increase glucose metabolism by 23 percent, which can help to prevent older age onset diabetes.
• Increases Bone Mineral Density: Resistance training has the same effect on bone tissue as it does on muscle tissue. Strength training triggers significant increases in mineral density and can help prevent osteoporosis.

Conclusion: Increasing Muscle Mass Lowers Your Risk of Death

The new UCLA study does have some limitations. For instance, the researchers aren’t able to definitively establish a cause-and-effect relationship between muscle mass and longevity. "But we can say that muscle mass seems to be an important predictor of risk of death," said Dr. Arun Karlamangla, an associate professor in the geriatrics division at UCLA and the study's co-author.

"In other words, the greater your muscle mass, the lower your risk of death," concluded Dr. Karlamangla. "Thus, rather than worrying about weight or body mass index, we should be trying to maximize and maintain muscle mass."

If you'd like to read more on this topic, check out my Psychology Today blog posts:

• “The Brain Drain of Inactivity”
• "What Is the Best Way to Improve Brain Power for Life?"
• “Scientists Discover Why Exercise Makes You Smarter”
• “Irisin: The ‘Exercise Hormone’ Has Powerful Health Benefits”
• “How Fit Are You? Your Answer May Reveal Dementia Risk”
• “Can Physical Activities Improve Fluid Intelligence?"
• “Yoga Has Potent Health Benefits”
• “Exercising at a “Conversational Pace” Is Good for Your Brain”
• “4 Lifestyle Choices That Will Keep You Young”
• “What Daily Habit Can Boost “Healthy Aging” Odds Sevenfold?”

Follow me on Twitter @ckbergland for updates on The Athlete’s Way blog posts.