The objective of the present meta-analysis was to evaluate the effects of variable protein intake in individuals submitted to resistance exercises, such as protein quality, dose-response, presence of leucine, and coadministration of carbohydrates. This review was conducted in pairs using the PubMed, Cochrane Central Register of Controlled Trials, and Embase databases. A total of 1115 articles were found, and 20 were included after the application of the inclusion and exclusion criteria. Protein ingestion subsequent to resistance exercise was shown to be effective in stimulating muscle protein synthesis (WMD 0.04 [95% CI 0.03, 0.04] P < 0.05). The ingestion of 20 or 40 g of whey did not show differences (muscle protein synthesis [MPS]; WMD −0.01 [95% CI −0.01, 0.00] P = 0.08), indicating that there is a saturation level in MPS capacity. The coadministration of carbohydrates with proteins did not show effectiveness in enhancing MPS (WMD 0.01 [95% CI −0.01, 0.03] P = 0.37). Leucine, when ingested with high-quality protein or a protein isolate, showed no additional effect (WMD 0.01 [95% CI −0.01, 0.002] P = 0.35), however seems to be the main amino acid involved in the stimulation of protein synthesis (WMD 0.04 [95% CI 0.03, 0.05] P < 0.05), and has a dose-response effect indicating a direction for future studies.