Meta study: whey reduces bodybuilders' body fat, has no effect on muscle mass
Whey supplementation improves the body composition of people who work out. In 2019 we wrote about a Portuguese study in which bodybuilders lost fat mass when supplementing with whey, but did not build up significantly more muscle mass. A Brazilian meta-study, published in Nutrients, comes to the same conclusion.Study
The researchers, who are affiliated with the Federal University of Grande Dourados, selected 10 studies from the scientific literature that they considered to be useful. In those studies, researchers got test subjects to do strength or fitness training, and gave them either whey or an isocaloric placebo.

Most test subjects were 18-30 years old, trained 2-5 times a week and, if they were in the experimental group, received 0.24-1.28 grams of whey per kilo of body weight per day. Some test subjects were athletes, some test subjects exercised sporadically.
The meta-analysis showed that whey supplementation caused a statistically significant decrease in fat mass. You can see that below. Click on the figures for an integral version.

The meta-study signaled a trend that supplementation with whey increased the fat-free mass [read: the muscle mass]. However, this trend was not significant.The Brazilians discovered the amount of whey the test subjects received, was not a factor in the muscle-building effect of whey. This also applies to the type of whey, or the test subjects' lifestye. It didn't matter if the test subjects were trained athletes or individuals with a sedentary way of life.
"This systematic review identified 10 randomized clinical trials in which whey protein supplementation was applied compared to isocaloric placebos in resistance training protocols", the researchers summarize.

"No significant effects were found to fat-free mass gain in any of the scenarios investigated, and a moderate fat mass loss was significant relative to whey protein supplementation by regular physical activity practitioners."
"Further randomized clinical trials based on this isocaloric approach are needed in order to provide more detailed evidence, especially regarding fat-free mass gain."
Nutrients. 2019;11(9):2047.