recently , the prevalence of obesity in the united states among young patients ( 319 years old ) with dm1 was found to be over 12%.1 for patients with dm2 and morbid or severe obesity , defined as body mass index ( bmi ) over 40 kg / m , bariatric surgery has resulted in reversal of type 2 dm in approximately 83% of cases.2 of the available bariatric surgical techniques , diabetes reversal ranges from 66% after gastric banding to 95% with the biliopancreatic diversion with duodenal switch ( bpd).3 there is increasing evidence that in addition to caloric restriction , significant changes in secretion of gut peptides or incretins occur with surgery leading to important enhancement of insulin production and utilization.4 in contradistinction to dm2 , results of these procedures in severely obese patients with dm1 are limited . czupryniak et al presented two cases of severely obese patients with dm1 who underwent roux - en - y gastric bypass surgery ( rygb ) . they reported remarkable improvement of glycemic control based on a decrease in glycosylated hemoglobin ( a1c ) of 9.5% to 5.7% in the first case and 10.4% to 7.3% in the second case . these authors suggested that rygb led to improvement in insulin resistance , favorably affecting glycemic control . nevertheless , insulin therapy was still required after 2 years in both cases although the insulin requirement decreased from 0.6 units / kg to 0.5 units / kg in the first case and from 0.95 units / kg to 0.78 units / kg in the second case.5 we retrospectively gathered data on three female patients with the diagnosis of dm1 with severe obesity that electively underwent rygb . the first patient ( patient a ) was a 29-year - old female with a history of dm1since age 21 . her diagnosis was confirmed by undetectable c - peptide ( < 0.1 ng / ml ) and elevated glutamic acid decarboxylase autoantibodies ( gad-65 ) at 4.1 nmol / l . since her last pregnancy at age 23 , her weight significantly increased to maximum preoperative weight of 115 kg ( bmi 40.6 she was unable to lose weight by lifestyle changes and was successfully screened for rygb . her average a1c the year before rygb surgery reflected poor glycemic control ( 8.2% ) . her total daily insulin dose before the surgery was 65.5 units , ( 0.57 units / kg ) . within the first month after the rygb surgery , her insulin requirements decreased to 0.37 units / kg without much prandial insulin on a very minimal diet . one year after the procedure her weight had decreased to 75.5 kg corresponding to a 34.4% weight reduction . her average a1c for the year after the surgery decreased to 7.5% . the second patient ( patient b ) was a 62-year - old female who had been diagnosed with dm1 since age 9 . undetectable c - peptide ( < 0.05 ng / ml ) was documented in her records confirming her diagnosis . her total daily insulin dose prior to rygb was 52.2 units ( 0.47 units / kg ) . one year after the procedure her weight had decreased to 77.5 kg ( 29.8% weight reduction ) . her total daily insulin dose had decreased to 35.6 units ( 0.46 units / kg ) . the third patient ( patient c ) was a 36-year - old female with a history of dm1 since age 22 . her diagnosis was supported by undetectable c - peptide ( < 0.05 ng / ml ) . she had history of obesity for at least 10 years before she was successfully scheduled for a rygb . at the time of her procedure her weight was 166.7 kg ( bmi 53.2 at one - year post procedure , her weight decreased to 96.4 kg for a 42.1% weight reduction . her insulin requirements had decreased to a total daily dose of approximately 48.2 units ( 0.5 units / kg ) . her average a1c for the year after the procedure increased to 8.8% ( tables 1 and 2 ) . the striking results of bariatric surgery on severely obese patients with dm2 have brought into question traditional theories on the pathogenesis and therapeutics of diabetes mellitus . complete resolution of this chronic condition is now the norm rather than the exception in severely obese patients that undergo bariatric procedures . extending these benefits to patients with dm1 growing research has offered several important facts and proposed theories to better understand this phenomenon . different bariatric techniques achieve different rates of dm2 diabetes resolution , with the most impressive results obtained from the partial gastrectomy with distal roux - en - y reconstruction ( rygb ) and the bpd . common endpoints of these techniques that use bypass procedure are rapid delivery of gastric content to the distal ileum and exclusion of proximal small intestine from the food path . rapid delivery of gastric content to the distal part of the small intestine has been associated with increased secretion of gut hormones also known as incretins . this concept also known as the hindgut theory proposes that incretins , especially glucagon - like peptide ( glp-1 ) and peptide yy ( pyy ) , contribute in great part to the improved metabolic control seen in the postoperative period.4 these two substances produced by the l cells of the distal ileum are known to have important metabolic actions . given the smaller plasma concentration of glp-1 compared to pyy , glp-1 is considered to be more potent . induced satiety through slow gastric emptying and action on the central nervous system has been linked to significant weight loss . more importantly , glp-1 has been associated with increased insulin secretion by acting directly over the beta cell membrane receptors . it also accelerates lipogenesis in adipocytes , which may result in improved insulin sensitivity.6 in addition , it has been shown in animal models with dm2 , that glp-1 increased beta - cell mass through regulation of proliferation , neogenesis , and apoptosis.7 this last quality of glp-1 would suggest a hopeful scenario for patients with dm1 of whom their residual beta cell mass is mostly minimal or absent . a different theory originally proposed by pories and later explored by rubino et al known as the  foregut bypass hypothesis , suggests that the exclusion of the duodenum and proximal jejunum from the gastrointestinal tract seems to prevent the secretion of a deleterious hormone ( decretin ) that could be implicated in the pathogenesis of diabetes.8,9 as to our knowledge , in despite of extensive research in this area bikman et al suggested that something other than the weight loss contributed in great part for the change in insulin utilization . they proposed that improved insulin sensitivity and greater glucose transport is related to reduced inhibition of b kinase  activity and enhanced insulin signaling in muscle.10 in this small series of patients with dm1 diabetes , the rygb bariatric procedure did not appear to significantly improve glycemic control . one year after the procedure , a1c was still not at goal for any of the three patients . insulin requirements did decrease for two patients suggesting improved insulin sensitivity , while it remained unchanged in one . we hypothesize that the resolution of dm2 after rgyb requires significant functioning beta cells mass . in dm1 where insulin secretion is minimal or often absent , rgyb is less likely to positively impact glycemic control . dependence of exogenous insulin therapy to achieve euglycemia precludes easily achieving optimal glycemic control in this patient population . the rygb bariatric procedure seems not to directly improve glycemic control in dm1 . achieving glycemic control is challenging in these patients even after decreasing their excess body weight and improving insulin sensitivity .
roux - en - y gastric bypass surgery ( rygb ) reverses type 2 diabetes ( dm2 ) in approximately 83% of patients with morbid or severe obesity . 
 this procedure has been performed in small numbers of severely obese patients with type 1 diabetes ( dm1 ) , but the impact on glycemic control and insulin requirement in this population has not been widely described . 
 we report three patients with dm1 and severe obesity that underwent rygb . 
 weight , glycemic control , and insulin requirements before and one year after the procedure were compared . 
 significant weight loss was achieved by all three patients but insulin requirements decreased in only 2 patients . 
 in contrast , glycemic control ( a1c ) remained suboptimal in all three patients up to one year after the surgery . 
 these findings suggest that rygb leads to important weight loss and positively affects insulin sensitivity . 
 however , reaching optimal glycemic control in patients with dm1 diabetes remains challenging due to persisting insulin deficiency .