Or maybe it was FOOD.
Exercise cannot make you gain weight.
The hormone response from training is negligible, and squatting doesn't hypertrophy any of the muscles it doesn't overload.
Squats and deadlifts (more than other exercises) cause a release of testosterone and growth hormone in the body during exercise, lasting until immediately afterward, then dissipating back to normal levels (Int J Sports Med. 1991 Apr;12(2):228-35). There isn't a lasting increase in these anabolic hormones (meaning, during periods of time where protein synthesis and muscle hypertrophy are actually occurring, anabolic hormone levels will be normal), and there have been no long-term studies on the affects of regular squatting and deadlifting in bodybuilders.
Growth hormone can be temporarily increased in the body from holding your breath or hyperventilating (Int. J. Sports Med. 7:311-315. 1986 ), should bodybuilders start believing this will make a difference in their physique?
A short anabolic response to exhaustive exercise doesn't mean you're now a super muscle building machine and all your muscle groups are gonna start blowing up, and it doesn't mean it can magically make you gain bodyweight.
I wish everyone would stop reading internet articles and PT sales pitches, and start thinking critically.