Four Buzzfeed staffers follow P90X3 for three months and report on their “gains.”

https://www.yahoo.com/health/we-worked-out-for-90-days-straight-and-this-is-118867976882.html

TL;DR
Starting advice to the 150 pound, 11% BF, 22 BMI male was there was “no need” to gain muscle mass or size, though it was suggested to the 140 pound, 8.8% BF male to gain a bit.

Results of 90 days were a few pounds lost among the females and a slight increase in size on the small male who is now almost 150 pounds (9 pounds gained) after three months. No report on any actual fitness or performance metric was taken or mentioned.