There are multiple factors associated with the production of IGF-1 in the human body. too few calories or protein deficiency can trigger a significant decline of the growth factor. Too many calories can lead to an increase of it. One study reported that normal weight women who consumed too many calories saw a 19 percent jump in IGF-1 after only 2 weeks of increased food consumption. Even worse they saw 46 percent of their overall body weight gain allocated to lean mass and a whopping 54 percent attributed to body fat. The women's testosterone levels increased dramatically while their fasting insulin was doubled. It isn't clear what contributed to the lean mass gain. It could be a result of the IGF-1, Insulin, testosterone or even all three. Excessive eating is not the best way to increase muscle mass. Remember, most of the weight the women gained was found to be in their body fat. This does help to rationalize the methods bodybuilders have used to gain mass in both the past and some in the present.
Here is one last study ( easy access link ), performed by Matthew Sharp and fellow researchers. Titled “The effects of a myostatin inhibitor on lean body mass, strength, and power in resistance trained males” from the Journal of the International Society of Sports Nutrition, the study also focuses on myostatin inhibitors when combined with resistance training. Unlike the study above, this one found the supplementation as “efficacious in increasing muscle mass in recreationally trained males” (Sharp et al., 2014).
This compound is designed to help people whose genetic makeup prevents them from acquiring significant muscle mass. This is because it also acts a myostatin inhibitor . Myostatin is a protein that inhibits the growth of muscle in the body. Some people naturally have a high amount of this protein in their bodies. Such people rarely acquire significant muscle mass even when they use available muscle building solutions. Thanks to yk-11, people who are naturally disadvantaged where muscle growth is concerned can also get to grow their muscles to the levels they desire.