People with HIV in Switzerland who started antiretroviral treatment after 2003 had less lipodystrophy—defined in this study as either fat loss in the face and limbs, fat gain in the trunk, or both—than those who started treatment between 2000 and 2002, say the authors of a new study published online by the British journal HIV Medicine. The authors credit a switch away from thymidine analogue drugs like Retrovir (zidovudine) and Zerit (stavudine) for much of the difference.

Researchers associated with the Swiss HIV Cohort Study examined the medical records of 6,016 Swiss HIV patients between 2000 and 2006. The researchers defined a new case of lipodystrophy as when a participant had rapid weight gain, rapid weight loss, accumulation of fat in the gut, or loss of fat in the limbs and face after starting HIV treatment.

At baseline, meaning the time of their first visit with a physician, 10 percent of participants already had fat loss, 10 percent had fat accumulation and 10 percent had both. Between 2003 and 2006, the use of Retrovir, Videx (didanosine) and Zerit decreased substantially. During the same period, use of Reyataz (atazanavir), tenofovir (found in Viread, Truvada and Atripla) and emtricitabine (found in Emtriva, Truvada and Atripla) increased substantially.

Over the course of the study, 10 percent of patients were diagnosed with only fat loss, 12.3 percent with only fat accumulation and 33 percent with either one or both measures. The percentage who developed lipodystrophy following HIV treatment initiation fell significantly between 2003 and 2006, and the percentage of people who changed or discontinued treatment because of lipodystrophy fell from 4 percent in 2003 to 1 percent in 2006.

The authors write, “We found that the probability of developing lipodystrophy had decreased [between 2003 and 2006], while the pattern of drug prescription had significantly changed.” They add, “While the use of thymidine analogues was almost universal in initial treatment in 2000, [Zerit] is no longer recommended in the guidelines for treatment initiation and had nearly disappeared by 2006, whereas [Retrovir] tends to be replaced by tenofovir.”

After controlling for a number of characteristics, researchers found that being older or black and having a high CD4 count were associated with more fat accumulation. Being older or female, having a high CD4 count or having taking abacavir (found in Ziagen, Epzicom and Trizivir) was associated with more fat loss. In previous studies, abacavir has been associated with gains in limb fat, and it should be noted that upon further analysis, the researchers of this study found that many people taking abacavir had switched to the drug after having taken another drug more commonly associated with limb fat loss.

Although certain drugs were associated with either fat accumulation—Crixivan (indinavir), efavirenz (found in Sustiva and Atripla), Viracept (nelfinavir) and abacavir—or fat loss—Reyataz, Sustiva, Viracept and abacavir—the authors caution that association in this study does not mean that any of these drugs can be seen as the cause of the fat accumulation or loss.