If you want to reach a ripe old age in good health, make sure you maintain your muscle mass. With age, muscle mass protects us against dying. At least, it’s possible to draw this conclusion from an epidemiological study that Swiss geriatricians published in Clinical Nutrition.
A little overweight healthy?
Three years ago a frequently seen headline in the mass media was A bit overweight? Then you’ll live longer! And in fact, there was nothing incorrect in the reports. They were a faithful representation of a study that American epidemiologists had published in JAMA. [JAMA. 2013 Jan 2;309(1):71-82.]
According to that study people with a BMI of between 25 and 30 have less chance of dying than people with a lower BMI. Sounds strange, doesn’t it? Scientists say that people with a normal lifestyle are healthiest when their BMI is between 22 and 24. So how come a bit of excess fat is healthy? Should anti-agers make sure they are on the plump side?
No, answered critical scientists, but people with a higher BMI may well also have more lean body mass – i.e. muscles. What’s more, a small amount of excess body fat can serve as a buffer in times of illness or psychological crisis, which would prevent breakdown of muscle mass. Muscle mass is a more positive health factor than body fat.
In the light of the illustrious JAMA study, the epidemiological study that the Swiss geriatrician Christophe Graf published in Clinical Nutrition is especially interesting. Graf collected data on 791 people over 65. In the period between 1990 and 2011 nurses had measured the body composition of these people at least twice.
Graf then ascertained who had died in the meantime and calculated whether there was a relationship between changes in body composition and the likelihood of death.
Graf discovered that increase or decrease in BMI did not alter the mortality risk. The same was true of increase or decrease of fat mass [call it the fat mass index, or FMI]. But a decrease in the fat free mass [i.e. fat free mass index, FFMI] did result in a significant increase in the chance of dying.
“This study highlights the negative impact of fat-free mass index loss on mortality in persons older than65 years, irrespective of sex, and age, comorbidities, and body composition at the last follow-up”, the researchers summarised. “It could not confirm that loss of BMI or fat mass index were related to increased mortality.”
“Future clinical and epidemiological studies should evaluate the impact of body composition and weight changes based on several measurements, and not on only two measurements, on mortality and evaluate whether maintaining fat-free mass index over time with physical exercise or anabolic strategies may improve survival.”
Impact of body composition changes on risk of all-cause mortality in older adults
This study evaluates the relationship between body mass index (BMI), fat mass index (FMI) and fat-free mass index (FFMI) changes and mortality in persons ≥65 years.
Adults ≥65 years with at least two body composition measurements (BCM) between 1990 and 2011 were included. We excluded persons who died within one month of the second BCM and who had two single BCM in a one-month timeframe. Mortality data was retrieved until December 2012. For each person, we calculated the regression slopes for BMI, FMI and FFMI changes. Significant positive slopes were categorized as “gain”, negative slopes as “loss” and the others as “maintenance”. The impact of body composition changes was evaluated by Cox regression models while adjusting for sex, age, co-morbidities and body composition at the last measurement.
We included 791 persons with 3049 BCM. After adjustment for sex, and age and co-morbidities, a loss of FFMI, but not of FMI or BMI, increased the risk of mortality (HR 2.02, 95%CI 1.28–3.19). The prediction of mortality with FFMI loss remained significant when further adjusting for FMI loss and the last available body composition (HR 1.68, 95%CI 1.04–2.70).
FFMI loss is related to increased mortality in older persons.