FRAM findings

Lipodystrophy-associated abdominal fat is ‘visceral’ rather than subcutaneous; i.e., it accumulates around the organs rather than under the skin. This visceral adipose fat (VAT) is also considerably denser than typical subcutaneous adipose fat (SAT) .

Increased VAT has been regarded as a core feature of lipodystrophy. However, the Study of Fat Redistribution and Metabolic Change in HIV Infection (FRAM) has observed that visceral abdominal fat accumulation is not, in fact, more common in HIV-infected men or women than it is in age-matched HIV-negative controls.^{1 2}

FRAM I enrolled participants between 2000 and 2002. FRAM II took a look at those participants four years later. A random sample of HIV-infected men and women seeking medical care in the US was used as a model on which to base the demographic characteristics of participants in FRAM.

The study found, unsurprisingly, that men with HIV had less subcutaneous fat (defined by DEXA scan), and those with lipoatrophy (defined by patient self-report and doctor's examination) had the smallest amount of subcutaneous fat. Subcutaneous fat loss was greatest from the legs, followed by the arms and then from the lower and upper trunk. ³

However, the findings relating to visceral fat accumulation were met with surprise. Men with HIV had less, not more, visceral fat than the control group. Men with lipoatrophy did in fact display a higher waist-to-hip measurement ratio; however, this was due to smaller hip measurements (likely due to loss of buttock fat), not bigger waistlines. ¹ Also surprisingly, buffalo hump was equally common in men with HIV and the HIV-negative control group, although the size of the humps was larger among men with HIV. HIV-positive men with buffalo hump also had significantly less subcutaneous trunk fat than HIV-negative men. ⁴

Lipoatrophy was also found more frequently in HIV-positive women than in HIV-negative controls (although less frequently than in HIV-positive men). Fat accumulation in central body regions was found to be comparably common in HIV-positive and HIV-negative women, and less common in HIV-positive women in peripheral body regions. ^1 5

There are two key interpretations from this study. The first, and most generally accepted, is that fat loss and fat gain in different parts of the body are not associated. This implies that peripheral body fat is not lost and redistributed to contribute to central fat accumulation, but that the two aspects (loss and accumulation) are separate processes with distinct causes, which may or may not occur simultaneously.

The other, and more controversial, interpretation is that lipoatrophy is in fact the only change specific to HIV-positive people, and that central fat accumulation may not be a defining characteristic of the syndrome at all. However, this challenges the findings of other studies, and the observations of many clinicians and people living with the syndrome. The cross-sectional FRAM study design, and lower baseline weight of HIV-positive participants makes it arguable that fat gains were unobserved by the study. Relatively small changes (similar to those experienced in the HIV-negative population) might become visible more easily in the HIV-positive group.