* Whey Protein * Studies (like this meta-analysis) have shown that whey protein increases upper and lower body lean muscle mass in people who perform steady resistance training. * Whey protein powders containing creatine increased this effect. * However, protein supplementation has shown to have little to no effect on muscle mass if you are already eating a high-protein diet. * Creatine * Studies (1)(2) have shown that creatine supplementation increases your performance, strength, and overall muscle mass. * Increases levels of IGF-1, a muscle-building hormone * Decreases the breakdown of proteins in your muscles * Increases water content in muscle cells (which prompts growth) * Beta-Alanine * Supplementing with this amino acid can improve your overall endurance during high-intensity interval training, leading to longer, more efficient workouts and increased lean muscle mass. * This study showed that beta-alanine supplements increased lean muscle mass among college wrestlers and football players (versus a placebo) * BCAAs (Branched-Chain Amino Acids) * BCAAs include leucine, isoleucine, and valine, which are naturally found in meat, poultry, eggs, dairy, and fish. * Research has shown that consuming BCAA supplements during a resistance-training regimen increases muscle strength and mass while boosting fat loss. * HMB (Beta-Hydroxy Beta-methylbutyrate) * Studies have shown that HMB supplements increased muscle mass in untrained adults. However, some have also shown that individuals with weight-training experience (seasoned lifters) did not experience significant muscle gain from HMB supplementation. * Reduces the breakdown of muscle proteins * Best used at or close to the time of exercise * Most beneficial for those just starting a resistance-training program