Hello, First of all, before most bariatric physicians will do surgery, the patient must prove that she has tried recently a nutrition weight loss plan of significan duration to learn about nutrition and to evaluate what the patient could do on her own. Secondly, regarding gastric bypass vs. gastric sleeve, there are differences to consider since your relative has diabetes. You want to avoid dumping syndrome as that could affect blood sugars dramatically. So, starting with the gastric bypass - a doctor will attach a small pouch to the intestines thus bypassing the stomach and limiting the amt. of intake, recovery time is about 2 weeks with no risk of dumping syndrome and the pt. can expect to lose 60-80% of their wt. in the first year to year and a half. A Gastric sleeve is where the surgeon actually removes part of the stomach producing a tube shaped stomach and thus the name sleeve , there IS a risk of dumping syndrome, recovery is 2-4 weeks (people with diabetes heal more slowly and have more wound complications), wt. loss is slower and steadier and in the first year wt. loss may be 50 - 80 percent. All patients have to follow a strict post-surgery diet that mandates nutritional skills in portion control, monitoring of blood sugar as med. adjustments may need to be made frequently, so be prepared to work intimately with a nutritionist. A physician can advise you further upon your first consultation for the surgery. I hope this answer has helped pave the way for future decisions and your visit with your surgeon. Thank you and have a GREAT DAY! K. Shattler, MS,RDN, Nutritionist