Some hair loss is to be expected after any weight loss surgery, but don't fret...it's only temporary! Hair loss can occur for several reasons. One is because the emotional, physical and hormonal stressors of surgery can cause the life cycle of your hair follicle to shift from Anagen (growth phase) to Telogen (rest phase). Hair follicles in the "Telogen phase" shed their hair more easily. Additionally, nutritional deficiencies like protein, zinc, biotin, iron, essential fatty acids, vitamin A and silica can also contribute to hair loss.
There are a couple things you can do to minimize hair loss:
1) stay up on your multivitamin recommendations
2) stay up on your protein intake recommendations
Good luck :)