Gastrointestinal Hormones and Appetite Ratings After Weight Loss by Diet or Bariatric Surgery

Background: It has been theorized that bariatric surgery's success can be partially explained by beneficial changes in gastrointestinal (GI) hormones, key regulators of eating behavior and homeostatic appetite control. Weight loss induced by dietary restriction is consistently shown to increase ghrelin concentrations and hunger ratings. The primary aim of this study was to compare initial changes in GI hormones and appetite ratings following a matched weight loss induced Sleeve Gastrectomy (SG) or Roux-en-Y Gastric Bypass (RYGB) or a very low energy diet (VLED). Ketosis is shown to modulate both GI hormones and appetite ratings, therefore a secondary aim was to investigate a potential association between magnitude of ketosis and changes these variables. Methods: Patients scheduled for SG (n=15) and RYGB (n=14), and 15 controls, matched for body mass index were recruited. Body weight/composition, basal plasma concentrations of β-hydroxybutyric acid (βHB), basal and postprandial plasma concentrations of acylated ghrelin (AG), total glucagon-like peptide 1 (GLP-1), total peptide YY (PYY), and cholecystokinin (CCK), as well as subjective ratings of hunger, fullness, desire to eat (DTE), and prospective food consumption (PFC) were measured before and after 10 weeks of weight loss induced by a VLED alone, or in combination with SG or RYGB. Results: No differences were seen in weight loss (-16%), any anthropometric variable, or magnitude of ketosis (βHB: 0.7 ±0.07 mM). SG and RYGB reduced basal and postprandial AG and increased postprandial GLP-1, controls showed no changes. Postprandial PYY increased for all. Basal and postprandial CCK were unchanged in SG and RYGB but declined in controls. Postprandial hunger ratings decreased in RYGB and controls, no changes for SG. SG and RYGB showed beneficial changes in DTE and PFC, while controls shpwed increased postprandial fullness. Greater increases in βHB concentrations was associated with larger reductions in fasting DTE, and greater βHB concentrations at W11 was associated with a larger reduction in basal GLP-1. Conclusions: Initial changes in ghrelin, GLP-1 and CCK following SG and RYGB are favorable compared to a VLED. However an overall reduction in appetite ratings were seen in all groups. This might reflect the fact that diet and magnitude of ketosis were matched across groups.