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Home arrow Health arrow Bariatric surgery patients: a nutritional guide


Patients with prediabetes and obesity need nutrition therapy but seldom receive it because it is an out-of-pocket expense. Prediabetes is a term used to convey that a person is at risk for diabetes with fasting blood glucose (FBG) of 100-125 mg/dL or 2-hour postprandial glucose level of 140-190 mg/dL [11]. Long-term use of antidepressant therapy and certain statin drugs can increase the risk of T2DM in the prediabetic population [11, p. 7].

Currently, metformin is the most widely prescribed antihyperglycemic agent and it is the first-line therapy for T2DM. Metformin lowers glucose by reducing the rate of hepatic glucose production, which can be significantly increased in T2DM due to poor food choices and inactivity. Since metformin does not cause hypoglycemia, it can safely be used in prediabetes, gestational diabetes, and PCOS [12].

The evaluation of gastric banding, gastric bypass, and sleeve gastrectomy in obtaining glycemic control is reviewed in numerous studies with the general outcome favoring gastric bypass and sleeve gastrectomy [13-20].

Cummings et al. conducted a trial known as Calorie Reduction or Surgery: Seeking Remission of Obesity and Diabetes (CROSSROADS) involving patients (body mass index [BMI]: 30-40) with T2DM. The benefits of bariatric surgery (gastric bypass) were significantly greater than medical and lifestyle interventions [21]. After 1 year, 60% of the gastric bypass patients were still in diabetes remission, whereas only 6% on the medical/ lifestyle program were in remission. Weight loss was greater in the gastric bypass group than in the nonsurgical approach group at 1 year.

Although the mainstay of treatment for T2DM has been pharmacologic and lifestyle modification, glycemic control through bariatric surgery has been associated with remission of the disease [22-25].

But the majority of the studies supporting bariatric surgery and diabetes remission have only short-term follow-up. A long-term study showing remission rates greater than 5 years was reported by Brethauer et al. in 2013 with partial or complete remission achieved in a percentage of T2DM individuals [26]. Those diagnosed <5 years with T2DM had a 76% remission rate compared with those diagnosed >5 years, with a 21% remission rate.

According to Panunji et al. in Diabetes Care, the major determining factor for diabetes remission and glycemic control is weight loss [27]. Remission rates were reported from 37%-95% based on surgical weight loss versus medical therapy and lifestyle changes. Since the International Diabetes Federation guidelines indicate bariatric surgery for patients with a BMI >40, those with a BMI of 35-40 are usually limited to medical therapy and lifestyle changes with little hope of remission.

Weight loss was cited by numerous studies as the primary factor for hyperglycemia management [28-30] and every effort needs to be made to assist T2DM patients with an opportunity for an effective weigh loss regime.

Dietary management for hyperglycemia focuses on avoiding excess sugar intake, reducing processed foods, and adding dietary supplements like chromium, vanadium, berberine, and cinnamon to help improve glucose control and insulin sensitivity. Addressing the deeper cause of glucose elevation, like gut inflammation, also needs to be considered.

Skipping breakfast has been shown to increase HgbAlc (Alc) and cause all day postprandial hyperglycemia in patients with T2DM. The extended fasting period created by skipping breakfast leads to reduced insulin and glucagon-like peptide-1 (GLP-1) levels, which decreases the activation of beta cells. This disruption of the circadian clock leads to increased postprandial glucose after lunch and dinner in T2DM patients [31].

T2DM is a complex and multifaceted disease requiring lifestyle interventions to achieve glycemic control but a recent study in JAMA reported improvement is better postbariatric surgery than with just lifestyle changes so health-care professionals need to stress bariatric surgery as a tool along with lifestyle changes [32]. Another study compared RYGB surgery with laparoscopic gastric sleeve surgery and a control group receiving intensive lifestyle weight loss intervention. Forty percent of the RYGB patients and 29% of the gastric sleeve participants achieved partial or complete remission of T2DM. Partial remission was defined as FBG <125 mg/dL and Alc <6.5% without medication and complete remission defined as FBG <100 mg/dL and A1c <5.7%, without medication. None of the lifestyle only participants had remission [33].

The efficacy of bariatric surgery in the treatment of T2DM is demonstrated by marked improvements in insulin sensitivity within the first few days after RYGB even before weight loss has occurred. However, long-term postoperative effectiveness was inconclusive due to limited follow-up research [34].

Xiong et al. monitored fasting GLP-1 and 2-hour GLP-1 values in a T2DM population. RYGB patients showed significant increase in GLP-1 and decreased fasting glucose-dependent insulinotropic polypeptide (GIP), which lead to improved glycemic control [35].

An LSG study reported in JAMA Surgery [36] indicates weight loss of 77%, 70%, 56% during the 1, 3, and 5 years of study respectively, with maintenance of complete remission of diabetes in 51%, 38%, and 20%, respectively, during that period. Hypertension and dyslipidemia were also improved but a significant weight gain occurred with longterm LSG patients.

Type 1 diabetes mellitus is increasing globally and leading to increased morbidity and mortality from obesity. Bariatric surgery achieved a significant improvement in insulin requirements but had only a modest effect on glycemic control in studies by Ashrafian and Mahawar [37,38].

Nutritional management for glycemic control focuses on a high-protein diet resulting in reduced liver enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT) along with a lower A1c [39]. Many studies have focused on the effects of the Mediterranean diet [40] but a recent study has indicated that a Nordic diet also can reduce the risk of T2DM. The Nordic food index is composed of six foods: fish, cabbage, rye bread, oatmeal, apples, pears, and root vegetables [41].

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