Gaining bulk is hard. I wish I had a nickel for every time I’ve seen a hardcore gym rat who’s been lifting for months, desperate for a few pounds of lean muscle mass, blow his stack when he hears a woman say, “Weight training will make me bulky.”
It takes a ton of energy for your body to add muscle. During the initial stages of any kind of intense training, especially one you’re not used to, your body releases excess amounts of the hormone cortisol, which causes your body to retain water. Some people think this means they are bulking up when, in reality, it’s just the body adapting to the training. It happens whether you are trying to gain or lose weight and has nothing to do with gaining actual muscle mass. Once your body adapts to the new training, the cortisol release ceases and your body flushes the excess water.
Now that being said, everyone is unique. Some people gain muscle quickly, while others are just naturally skinny. Your Body Type plays a critical role in how your body will react. This can easily be assessed.