A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: A randomized human clinical study 

This randomized, placebo-controlled, double-blind, parallel-arm study evaluated a whey protein supplement, high in leucine, bioactive peptides and milk calcium, for its ability to enhance weight loss in study participants, along with a 500 calorie reduction per day. The results show that both groups lost a significant amount of weight from baseline, with the supplementation group losing more weight than the placebo group after 12 weeks of supplementation. The supplementation group lost significantly more body fat and less lean muscle than the placebo group, with the ratio of fat to lean loss much larger in the supplementation group. 

References;

 Frestedt JL, Zenk JL, Kuskowski MA, Ward LS, Bastian ED. A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: a randomized human clinical study. Nutr Metab (Lond). 2008 Mar 27;5:8. doi: 10.1186/1743-7075-5-8. PMID: 18371214; PMCID: PMC2289832.