Weight Loss Surgery and The Long-Term Impacts for Patients with Diabetes

Weight loss surgery may change the way the brain responds to food cues. 

Often a focus of care for patients with diabetes is their BMI and consequently their weight. Lifestyle factors such as diet and exercise are incredibly impactful in reducing symptoms of type 2 diabetes. Many patients who undergo weight loss surgery also have diabetes. The most effective way to reduce a patient’s A1c is by altering a patient’s diet and exercise. Many patients with diabetes have used a very low-calorie diet (VLCD) to lose weight and cause remission of their diabetes. However, most patients regain all the weight they have lost within a year, thus suggesting a VLCD is not sustainable. Another option for weight loss is surgery like gastric bypasses, such as Roux-en-Y gastric bypass surgery (RYGB). An article by Salem et al. explores the differences in a VLCD and gastric bypass regarding sustainable weight loss. Several studies have been conducted to collect data correlating a change in brain activation and bariatric surgery. However, there is not much data relating to brain activation and bariatric surgery in patients with diabetes or prediabetes. Additionally, there is no research about the long-term impacts of weight loss on a diet compared to bariatric surgery. Salem et al. “hypothesized that in patients living with obesity and prediabetes/T2D, longitudinal changes in brain activity in response to food cues as measured using functional MRI would explain this difference.”  

This study recruited 16 participants already planning to undergo gastric bypass surgery and 19 willing to follow a VLCD (800kcal/day) for four weeks. All participants were non-insulin requiring patients with T2DM and had a stable A1c of <9%. Other exclusion criteria were smoking, comorbidities, pregnancy, a history of eating disorders, and any medication that could compromise the study’s validity. An fMRI scan was performed twice, first at the initial visit and then at the second visit during week 4. According to Salem, “At arrival, before, and after the MRI scan and then before and after lunch, participants completed a 100-mm visual analog scale (VAS) that rated nausea and pleasantness to eat. In addition, at each visit, fasting blood samples for gut hormones were collected in lithium heparin tubes containing aprotinin (Nordic Pharma, Reading, U.K.) and a dipeptidyl peptidase four inhibitors Diprotin A (20 µg/mL blood; Enzo Life Sciences, Exeter, U.K.).” 

The fMRI was performed while the patients were shown a series of food images. A gray screen separated those images for a certain period to separate the response data. The photos that were shown were of both bland and flavorful foods. This exercise aimed to determine if there was any difference in brain signaling between patients on a VLCD or those who underwent gastric bypass surgery. Depending on the tested hypothesis, the researchers picked functional and anatomical areas for each region of interest (ROI). Most were related to food cue responsiveness and hedonic reward network (insula, amygdala, putamen, caudate, nucleus accumbens, orbitofrontal cortex) and were chosen because of their use in similar studies. 

The study results provided a great deal of evidence that the participants on a VLCD showed an augmented response to food cues compared to those who had gastric bypass. “At 12 months, the VLCD group regained all the weight previously lost, while the RYGB group continued to lose weight” (Salem et al.). This information is directly related to the pleasure centers in the brain and has implications as to why a VLCD is not sustainable for a patient. Following RYGB-induced weight loss, the appetite system located in the hypothalamus is more active but showed reduced response to food cues. The same level of activation was not present in patients who followed a VLCD to lose weight. This information suggests that the brain activation experienced by RYGB patients may reduce weight regain compared with patients following a VLCD. However, these patients were not studied on a longitudinal basis, so there is no data on any other changes in lifelong brain activity.  

Practice Pearls:  

•  A very low-calorie diet does not provide sustainable weight loss for patients with diabetes.  
•  Weight loss surgery, such as gastric bypass, can provide a means to successfully sustainable weight loss.   
• The difference between a VLCD and weight loss surgery ties to the reward center in the brain, thus making the sustainability of each differ from the other.  

Jones, Ben, et al. “The Metabolomic Effects of Tripeptide Gut Hormone Infusion Compared to Roux-En-y Gastric Bypass and Caloric Restriction.” The Journal of Clinical Endocrinology & Metabolism, 2021,  

Salem, Victoria, et al. “Weight Loss by Low-Calorie Diet versus Gastric Bypass Surgery in People with Diabetes Results in Divergent Brain Activation Patterns: A Functional Mri Study.” Diabetes Care, vol. 44, no. 8, 2021,  

Grace Behr, PharmD/MBA Candidate, Creighton University