The main objective of the study is to measure changes in blood lipids during 48 weeks of treatment with saquinavir (SQV) / ritonavir (RTV) or atazanavir (ATV) / RTV, in combination with tenofovir (TDF) / emtricitabine (FTC). All of these medications are commonly used for the treatment of HIV-1 infection. When the initial anti-HIV therapy is selected, several important issues are considered such as the effectiveness, the possible long- and/or short-term side effects, the frequency of medication intake and the amount of pills that needs to be taken.