Hopefully they have talked to you in great detail about food choices that you will need to follow, since this can be a part of this lose. Protein is essential for hair follicle health, so gastric bypass really effects how you digest and break down protein, so you will need to look at a protein powder and use this on a daily basis to maintain protein status. With this protein, the follicle will need biotin, b-vitamins (you will need to do B-12 separately as an under the tongue lozenge, since your B-12 breakdown will be changed) and omega 3’s (preferably fish oil, since digestion of fats is also compromised with gastric bypass so flaxseed breakdown will be difficult). I recommend Biotin Forte from Integrative Therapeutics, since this is Biotin and B vitamins together and it is a high potency. A B-12 of at least 1000mcg daily dissolved under the tongue, not only is this important for the body, but great for metabolism. A fish oil with Vitamin D would also be great and I would recommend a fish oil with an EPA>1200mg and a DHA>900mg. The vitamin D will be helpful to the thyroid and since this system can show hair lose if compromised the D will help here. I am a big believer in strong, health organs of elimination, kidney, liver, gastro-intestinal tract, and when one is compromised the other two will have to take on more work. Another place where hair health is seen is in the kidneys, so if the above options do not do all we need them to do, then we will need to look further. Good Luck.