Really sleepy after workouts.

Marmalina

Even on days that I don't work out as intensely...right after, i honestly feel like I could use a nap. I get really tired and don't have the energy in me to do anything. I usually go to class right after and it takes everything in me to get ready to go. This is really weird for me because when I first started working out, I would feel more energized. I always follow each workout with some sort of protein smoothy with freshly blended fruits, so I don't think its that...and I go to the gym about an hour after breakfast. What could be making me feel this way?