The objective of this cross-sectional study was to assess the nutritional status of HIV-positive patients in a hospital in the city of Niteroi, Rio de Janeiro, Brazil. We studied 235 patients (130 men and 105 women) from May 2009 to June 2010. The frequency of undernourishment among women was 7.6%; 26.7% of the women were overweight, and 16.2% were obese. Among men, the frequency of undernourishment was 3.8%; 25.4% of the men were overweight, and 6.9% were obese. A logistic regression was done to investigate the relationship between nutritional status and potential predisposing factors. Women were more frequently affected by obesity and undernourishment than men. However, only the difference in obesity was significant, and women had almost three times higher odds of being obese (OR 2.6; 95% CI 1.03-6.65). According to a nationwide survey done in Brazil during 2008-2009, 50.1% of the Brazilian healthy males were overweight, and 12.5% were obese; 48% of healthy females were overweight, and 16.9% were obese. Although the prevalence of undernourishment in HIV-positive patients is now lower than that observed in the beginning of the AIDS epidemic and excess weight is increasingly common among people living with HIV/AIDS, the proportion of excess weight was found lower and of undernourishment was higher in the present study than that found in the Brazilian population.