History and background

Lipodystrophy was first observed during 1997 among people who had been taking protease inhibitors for several months. Unofficially referred to as 'Crix belly', the syndrome was reported as abdominal weight gain among people taking indinavir (Crixivan). However, this was largely a consequence of the fact that indinavir was by far the most widely prescribed antiretroviral agent at that point in time. Subsequently, the syndrome was linked to protease inhibitors as a class of drugs, with anecdotal reports in people taking combinations that did not include protease inhibitors, and even in those not on any form of treatment.

Abnormal body fat changes were seen to occur over and above those that might be expected in people recovering from serious illness, even taking into account the reduced resting energy expenditure requirements of people who no longer had high levels of HIV replication. (HAART typically reduces such requirements by about 10% once undetectable viral load is reached.) If resting energy expenditure declines without a reduction in food intake, the result is weight gain in the form of fat.¹