Study participants who were males (AOR: 1.35, 95% CI: 1.16–1.56), had tuberculosis (AOR: 2.17, 95% CI: 1.56–3.02), anaemia (AOR: 1.21, 95% CI: 1.04–1.40), CD4 counts ≤ 200 cells/μL (AOR: 1.34, 95% CI: 1.17–1.54), viral load ≥ 100,001 copies/ml (AOR: 1.21, 95% CI: 1.04–1.40), and WHO Clinical stages 3 and 4 (AOR: 1.33, 95% CI: 1.15–1.53) at presentation to the ART clinic were associated with actual weight gain at their 6-month follow-up clinic visit. This evidence concerns the gene CD4 and tuberculosis.