Abstract Objectives: The main aim of this study was to assess the association between BMI and progression of AIDS as well as examine the association between biochemical markers and AIDS progression. In addition, to analyze the nutritional factors that could increase/decrease the progression of AIDS among patients in the kingdom of Bahrain. Method: A retrospective cohort study, including all individuals with HIV/AIDS having a medical record at Salmaniya Medical Complex (SMC) at the kingdom of Bahrain. Various biochemical markers were collected from patients' files including CD4+ T cells counts, albumin, hemoglobin, MCV, WBC, and creatinine. In the period from August 5th to October 5th, 2021, participants were contacted and asked to answer a semi- structured questionnaire that consisted of a standardized food frequency questionnaire (FFQ). The FFQ were analyzed and stratified to obtain total energy and total macronutrients intakes as well as daily dietary pattern. BMI were calculated as weight in kilograms divided by the square of height in meters (kg/m2). The obtained BMI values were stratified into the WHO criteria: <17 (moderate to severe malnutrition), 17 to<18.5 kg/m2 (mild malnutrition), >18.5 to 25 kg/m2 (normal nutrition) and >25 kg/m2 (overweight and obese). The collected data were entered into Statistical Package for Social Science (SPSS). Bivariate analysis and multiple logistic models were used to show the relation between malnutrition and various associated factors. Confidence interval of 95% was used to find out the precision of the study and the level of significance was taken at p <0.05. Results: It was found that the mean BMI of participants 27.20 kg/m2 with the following BMI classification frequencies, 38.27% normal-weight, 37.03% overweight, 18.51% obese class I, 4.93% obese class II, and 1.23% obese class III. Mean of total calories intake was 2232+509.96 Kcal/day for males and 2290+425.46 Kcal/day for females. Mean total proteins, total carbohydrates and total fats for males was 66.76+36.36 g/day, 36.36+10.92 g/day, and 364.04+73.46 g/day respectively. Mean total proteins, total carbohydrates and total fats for females was 65.35 +11.70 g/day, 37.04+7.74 g/ day, and 333.18+87.68 g/day respectively. Statistically significant correlation between BMI and total calories (r=0.47, p-value<0.00), total carbohydrates (1=0.74, p-value <0.00), total proteins (r=0.71, p-value<0.00), and total lipids (r=0.70, p-value <0.00). Mean CD4+ T cells counts was 620+673.40 cells/mm3, albumin 42.77+5.62 g/L, hemoglobin 13.51+2.31 g/L, MCV 83.13+10.28 g/L, WBC 6.16+2.59 x109/L, HTC 42.15+7.03%, and creatinine 84.19+57.28 mg/dL. Biochemical alterations related to AIDS progression in association to nutritional factors were detected in various percentages among the study population. Participants (45.85%) represented with CD4+ T cells counts of ≤ 500 cells/mm3, low hemoglobin and HCT levels represented in 20.74% of participants, hypoalbuminemia was represented in 5.09%, low levels of WBC represented in about 26.87%, and elevated creatinine levels were represented in 5.72%. In addition, correlating the biochemical markers in comparison to each other showed a significant positive correlation of CD4+ T cells counts, hemoglobin, HCT and albumin at <0.05 level. There was no significant correlation between CD4+ T cells counts MCV, WBC and creatinine. A positive significant correlation was found between BMI, CD4+ T cells counts, and WBC at <0.01 level. Conclusion: It was determined that BMI values were significantly correlated to biochemical markers of AIDS progression. Dietary pattern of participants was found to be undiversified among participants, with high prevalence of obesity and overweight. Malnutrition among this study population was not present when compared to higher prevalence of malnutrition amongst AIDS patients in other developing countries. This information offers the initial step towards future studies that can provide detailed results.