My GP said the hair loss associated with bariatric surgery is called telogen effluvium and has to do with the normal hair growth cycle. The web explains it usually starts abruptly and very seldom lasts longer than 6 months. Human hair has a two stage growth cycle. The growth phase is called anagen and 90% of our hair follicles are in this phase at any given time. The resting phase is called telogen, which lasts about 1 to 6 months, with an average of 3 months. About 5-15% of our hair is in the resting phase at any given time. It is also known that telogen effluvium has to do with stress to the body and hormonal changes that can occur. Due to the stress more hair follicles can enter into the resting phase. This is important because the hair in the resting phase at the time of surgery is most likely the hair you will shed. This is why your hair sheds between 1 to 6 months after surgery (usually about 3 to 4 months). When the hair starts to grow again the old hair follicle is released and you lose hair. Sometimes the hair comes out before new hair grows, yikes!
So in summary, this type of hair loss is a diffuse shedding of hair as it relates to the normal hair growth cycle. It is common in men and women and all races. It occurs a little more frequently in women typically after child birth.
Why does this happen in people who have bariatric surgery? The most common reasons are:
Surgery, acute illness, trauma
Chronic disease such as liver disease or any chronic debilitating disease
Hormonal imbalance such as hypothyroidism
Crash dieting, low protein intake, anorexia, chronic iron deficiency
Heavy metal toxicity
Medications such as beta-blockers, excess vitamin A and anticoagulants.
So, what we have here are a few things that may be affecting people with hair loss. It starts with surgery, a very low calorie intake and possibly low protein intake. Then you add any illness along the way, an underactive thyroid, iron deficiency, or genetics and you get hair loss of about 5-15% of your hair follicles. Other nutrients implicated in hair loss include zinc, biotin, folate, vitamin B-6 and essential fatty acids. If no deficiency of these nutrients exists, then they will likely be of little use.
The good news is that you can count on the hair returning unless you have a chronic illness or genetic reason for the hair thinning.