I don’t wish to appear fixated on fat, but another paper on the relationship between obesity and survival has appeared. This one is easier to understand than those that have preceded it. The Obesity Paradox and Mortality Associated With Surrogates of Body Size and Muscle Mass in Patients Receiving Hemodialysis examines if an increase in dry weight accompanied by an increase in muscle mass is associated with a survival benefit in patients receiving maintenance hemodialysis (HD). The short answer is yes.
While the graph above (click on it to see it full size) shows that the higher the BMI the lower the morality rate this not a simple function of weight gain, but rather reflects an increase in muscle mass. This interpretation is supported by the observation that patients who lost weight but had an increased serum creatinine level had a greater survival rate than those who gained weight but had a decreased creatinine level. Serum creatinine in this context is a surrogate for increased muscle mass.
The authors conclude: In patients receiving long-term HD, larger body size with more muscle mass appears associated with a higher survival rate. A discordant muscle gain with weight loss over time may confer more survival benefit than weight gain while losing muscle. Controlled trials of muscle-gaining interventions in patients receiving HD are warranted. The last sentence is key. Just because increased muscle mass is associated with increased survival doesn’t necessarily mean that inducing an increase in muscle mass by altering diet and prescribing an appropriate exercise regimen will lengthen life in dialysis patients.