Introduction: The literature has been controversial regarding the benefits of testosterone replacement in obese men with low androgen levels. Uncontrolled studies have shown that testosterone therapy resulted in substantial and sustained reductions in bodyweight, waist circumference (WC) and body mass index (BMI), but controlled studies have showed no significant changes in these antropometric parameters between treated and untreated patients.
Objective: The objective of this systematic review was to evaluate from randomized controlled trials (RCT) the effectiveness and safety of testosterone replacement in obese men with low testosterone levels. Methods: The primary outcomes were weight loss, quality of life, improvement of obesity comorbidities, frequency of cardiovascular events, deaths, and adverse events. Search strategies were applied to MEDLINE, EMBASE, LILACS, CENTRAL, Scopus, and Trip databases. Two reviewers independently selected the studies, assessed the risk of bias, and extracted data. The relative risk (RR) and mean difference (MD) were calculated with a 95 % confidence interval (CI) as effect size of testosterone, and a random-effect model was used for the meta-analysis. The Grading of Recommendations Assessment, Development, and Evaluation system was used to evaluate the certainty of evidence. Results: Eighteenteen RCTs were included. Compared with no replacement, testosterone improved total lean body mass and decreased WC (MD 1.88 kg, 95% CI, 1.28 to 2.48, 465 participants, 7 studies; MD -2.31 cm, 95% CI -3.52 to -1.1, 1250 partcipants, 14 studies, respectively, moderate certainity of evidence), but did not have effect on body weight and BMI. Due to imprecision and inconsistency, no clear effect was observed between intervention and cardiovascular events, as well as for quality of life and obesity comorbidities. We found no significant difference in the frequency of adverse events (RR 1.05, 95% CI, 0.70 to 1.56, 624 participants, 8 studies, moderate quality of evidence). Conclusion: In obese men with low levels of testosterone, its replacement might be safe, improves total lean mass, decreases WC, however, does not have effect on body weight and BMI. For cardiovascular events, quality of life, obesity comorbidities, the effect was uncertain. PROSPERO (registration number: CRD42017065598)