Anti-HIV agents. Efavirenz and fat wasting--what might be happening?

A question that immediately arises is: Why did the combination of lopinavir/r + efavirenz result in the lowest level of lipoatrophy? Part of the answer may be that no nukes, particularly thymidine analogues such as d4T or AZT, were present. Also, test-tube research done in Canada and France suggests that ritonavir may be able to stimulate the growth of fat cells and, perhaps, counter the effect of efavirenz. This requires further laboratory study with experiments on fat cells, comparing the effect of lopinavir, ritonavir and efavirenz.