# A Western-Style Diet Influences Ingestive Behavior and Glycemic Control in a Rat Model of Roux-en-Y Gastric Bypass Surgery

## TL;DR

This study shows that diet after gastric bypass surgery affects weight loss, eating patterns, and blood sugar control in rats.

## Contribution

The study reveals how diet type interacts with gastric bypass surgery to influence ingestive behavior and glycemic outcomes in rats.

## Key findings

- Rats on a Western-style diet showed enhanced weight loss after surgery but had similar body weights to low-fat diet rats post-surgery.
- Gastric bypass surgery improved glycemic control but its effects were influenced by diet, especially in high-fat diet groups.
- Diet significantly impacted meal patterns, glucose regulation, and beta-cell sensitivity after surgery.

## Abstract

Background: Roux-en-Y gastric bypass (RYGB) surgery results in weight reduction and decreased energy intake and can ameliorate type 2 diabetes. These beneficial effects are usually attributed to changes in hunger and satiety and relatively rapid improvements in glycemic control, but these effects may depend on dietary adherence. The aim of this study is to investigate the relatively early effects of RYGB surgery on weight reduction (by focusing on eating patterns) and glycemic control in rats subjected to a healthy maintenance diet or an unhealthy Western-style diet. Methods: Rats were fed a high-fat diet with added sucrose (HF/S) or a low-fat (LF) diet. Body weight, high-resolution tracking of meal-related parameters, and glucose regulation after overnight fasting and during a mixed meal tolerance test (MMTT; 2 mL sweet/condensed milk) were measured before and after RYGB (RYGB+) or sham surgery (RYGB−). Results: HF/S feeding led to an increased body weight just before RYGB surgery, but it also caused enhanced weight loss following RYGB, which led to similar body weights in the HF/S and LF diet groups twenty-four days post-operatively. RYGB surgery and diet dependently and independently influenced meal-related parameter outcomes, where both RYGB+ and HF/S feeding resulted in shorter meal duration (p < 0.01), higher ingestion rates (p < 0.001), and increased satiety ratio (p < 0.05), especially in the HF/S diet group subjected to RYGB. While RYGB surgery generally improved baseline glycemic parameters including HOMA-IR (p < 0.01), it often interacted with diet to affect MMTT-induced hyperglycemia (p < 0.05), beta-cell sensitivity (p < 0.01), and the insulinogenic index (p < 0.01), with the LF rats overall maintaining better glycemic control than the HF/S-fed rats. Conclusions: This study shows the importance of controlling diet after RYGB surgery, as diet type significantly influences ingestive behavior, post-prandial glucose regulation, beta-cell sensitivity, and glucose tolerance after RYGB.