Background: Roux-en-Y gastric bypass (RYGB) leads to effective and sustained weight loss whereas a Very-Low-Calorie diet (VLCD) is normally plagued by weight regain over time. Changes in gut hormones following each intervention may play a role. The aim of this study was to investigate gut hormone responses after 4 weeks of RYGB and VLCD.
Methods: We prospectively recruited 21 volunteers with obesity and type 2 diabetes undergoing RYGB, and a matched cohort of 22 volunteers who underwent a VLCD of 800 kcal/day for 4 weeks. A mixed meal test, with sampling for gut hormones, was administered before and after 4 weeks of the interventions. Subjective feelings of hunger, fullness and volume were recorded using Visual Analogue Scales (VAS).
Results: Weight losses following RYGB and VLCD at 4 weeks were similar at −10.3 ± 0.7 kg (−8.8 %) and −8.3 ± 0.6 kg (−7.6%) respectively. A drop in HbA1c of 8.4 ± 1.1 mmol/mol for surgery and 7.0 ± 0.8 for VLCD was observed. Post-prandial levels of GLP-1, PYY and Oxyntomodulin were augmented after RYGB, with significantly higher peak levels at 30 min after the meal, while ghrelin levels were reduced. In contrast, fasting ghrelin levels were increased after the VLCD whereas GLP-1, PYY, Oxyntomodulin and GIP remained unchanged. Fasted hunger and volume VAS scores were reduced while fullness scores were enhanced with surgery but were unaffected following the VLCD. After one year, RYGB subjects continued to lose weight (mean −29.5%) with a further drop in HbA1c (9.2 ± 1.3 mmol/mol). In contrast, VLCD subjects regained most of their initial weight loss (−1.9%) with their HbA1c back to pre-intervention level.
Conclusion: Anorectic gut hormones may play a key role in promoting the sustained weight loss in RYGB whereas the increase in ghrelin may contribute to the lack of sustained weight loss in VLCD.