I know, I know.

If the current state of knowledge was not enough to get you into the gym and lifting weights (or at least doing serious bodyweight progressions) a powerful new study is not enough. We are up against the limits of bounded rationality.

Nevertheless, a new study puts muscle mass as a powerful predictor of longevity and all cause mortality.

It’s more interesting than ever, because obesity, in its itself has not been a powerful predictor in older adults. In fact, for older adults obesity alone is not associated with increased mortality.

The study was published in the American Journal of Medicine: “However, adiposity and muscle mass have opposite associations with glucose metabolism and health risks, and thus possibly opposite associations with mortality risk. Because old age is a time of changing balance be- tween fat and muscle mass, total body mass (and BMI) becomes less useful in assessing the metabolic health of older adults. In contrast, waist hip ratio, which indirectly reflects the relative abundance of central fat over peripheral fat and muscle (specifically, gluteal muscle), does have positive associations with all-cause mortality even in older individuals. A few studies also have found that muscle strength is related inversely to mortality risk in older adults.”

  • Muscle mass is associated inversely with mortality risk in older adults independently of fat mass and cardiovascular and metabolic risk factors.
  •   Anabolic processes that promote muscle bulkmay be associated with longer survival.Changes in body composition, rather than adiposity alone, should be considered when counseling older adults on preventativehealth behaviors.

“As hypothesized, in older Americans, muscle mass relative to body height was associated inversely with all-cause mortality over a 10- to 16-year follow-up. This inverse relationship was not explained by traditional cardiovascular risk factors (dyslipidemia, hypertension, and inflammation) or glucose dysregulation (pre-diabetes, diabetes, insulin resistance, and dysglycemia), suggesting that relative muscle mass is an independent prognostic marker for survival in older adults.

Traditional cardiovascular risk factors and glucose dysregulation are linked to the development of atherosclerotic vascular disease and reduced cardiac output, which in turn lead to reduced blood flow to skeletal muscle, and thus, potentially, to reduced muscle mass. The cardiovascular risk factors and markers of glucose dysregulation and inflammation in this study may not have completely captured the extent of subclinical cardiovascular disease, and the independent prognostic ability of relative muscle mass may be a reflection of the mortality risks conferred by subclinical cardiovascular disease in older adults.

Alternately, factors that lead to better than average relative muscle mass, such as genetic predisposition and aconsistently active lifestyle over the life-course, also are likely to increase cardiorespiratory fitness, a major predictor of improved survival. The survival prediction ability of relative muscle mass may simply reflect the protective role of cardiorespiratory fitness. Finally, a potential causal pathway from muscle mass to longevity is through the role of muscle as a reliable protein reserve, which is vital in protecting an individual after a prolonged illness.

Even if there are no causal links between muscle mass and longevity, this study definitively demonstrates that muscle mass relative to body height has independent predictive ability for all-cause mortality in older adults. This is the first study to establish this in a large, nationally representative cohort. Previous studies have uncovered associations between muscle function (strength, power, speed) and mortality, but have failed to find associations between muscle bulk and mortality.”

“This study establishes the independent survival prediction ability of muscle mass as measured by bioelectrical impedance in older adults, using data from a large, nationally representative cohort. This is in sharp contrast to BMI, whose association with mortality in older adults is inconsistent, at best. We conclude that measurement of muscle mass relative to body height should be added to the toolbox of clinicians caring for older adults. Future research should determine the type and duration of exercise interventions that improve muscle mass and potentially increase survival in well, older adults.”

Since it gets harder and harder to put on muscle with age, the conclusion is clear. Hit the gym today.

see the full study here: