Lower Limb Fat, Higher Belly Fat Associated With Mortality in People With HIV; BMI Measurements Questioned
March 28, 2011
The following is our transcript of a press conference that took place on March 1 at CROI 2011. In it, Rebecca Scherzer, Ph.D., summarized the findings of a study she was presenting at the conference entitled, "Decreased Limb Muscle and Increased Central Adiposity Are Associated with 5-Year All-cause Mortality in HIV Infection." The study's chief finding is that decreased muscle mass and increased central fat appears to be associated with mortality risk in people with HIV -- a risk that current body mass index measurements may fail to detect.
Rebecca Scherzer: The subject of my talk today was the relationship of body fat and muscle with mortality in HIV infection. We know that unintended weight loss and muscle loss due to disease and aging are risk factors for mortality. Even today, when effective antiretroviral therapy is widely available, we know that HIV-infected patients remain at higher risk of death compared with uninfected persons.
I reported results today from FRAM, the Study of Fat Redistribution and Metabolic Change in HIV Infection. We used whole-body MRI [magnetic resonance imaging] to measure fat and skeletal muscle in nearly 1,200 HIV-infected adults. At our follow-up exam five years later, we determined how many study participants were still alive.
We found that decreased muscle in the arms and legs and increased belly fat were strong and independent predictors of mortality, even after we control for other factors that might be associated with mortality, such as traditional cardiovascular risk factors, HIV-related factors, and markers of inflammation and renal disease.
Contrary to our expectation, we found that peripheral lipoatrophy -- that means loss of leg fat -- which has been reported in HIV infection, did not predict mortality. The relationship between muscle wasting and survival is well known, but clinicians don't measure muscle mass. Instead, clinicians usually rely on body mass index, or BMI, to determine whether a patient has HIV wasting.
Someone with excess belly fat and decreased muscle is at greater risk of death, according to our study. However, such a person might still have a normal BMI, due to their increased belly fat. This illustrates that BMI is a flawed measure. Also keep in mind that muscle is more dense than fat, so it weighs more. So at the other end of the spectrum, if you rely on BMI, you're going to classify someone with a lot of muscle, like an NFL [National Football League] linebacker or Arnold Schwarzenegger, as obese. So it's flawed at both ends.
We'd like to see clinicians use waist circumference as a simple measure of belly fat, and consider estimating arm muscle, using mid-arm circumference and triceps skin fold.
In summary, you do need to track weight change, but also be aware that patients with large bellies may not necessarily have a low enough BMI to alert you to their true risk level. In other words, losing weight is only a signal. Therefore a careful evaluation of the muscle status in patients with excess belly fat is warranted. Thank you.
Reporter: You gave some indication; you talked a little bit about how clinicians should deal with this issue. And I just wonder if you could elaborate on that a little bit. You're right: Most doctors look at BMI. So what else? How should they deal with this? How alert should they be to this issue?
Rebecca Scherzer: We think, in particular, patients who have increased belly fat; those, perhaps, should be the first ones that you'd want to look at, and start to evaluate their muscle status.
Belly fat can be very easily assessed by measuring waist circumference. There are established cut points. I can't tell you one offhand, but the various diabetes groups have published these, so you can tell who is elevated, based on that.
The problem is that the combination of low arm muscle and increased belly fat may lead to somebody having a fairly normal BMI, where you wouldn't ordinarily be worried about HIV wasting.
This transcript has been lightly edited for clarity.
Copyright © 2011 The HealthCentral Network, Inc. All rights reserved.
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