OBJECTIVES: Altered appetite-related gut hormone concentrations may reflect a physiological adaptation facilitating weight regain after weight loss. This review investigates hormonal changes after weight loss achieved through calorie restriction (CR), exercise (EX), or both combined (CREX). METHODS: A systematic search of PubMed (MEDLINE), EMBASE, SPORTDiscus, Cochrane Library, Web of Science, and ClinicalTrials.gov was conducted to identify randomised controlled trials (RCTs) and non-RCTs reporting in a fasting state either pre- and post-intervention appetite-related hormone concentrations or the changes therein after weight loss. The hormones examined were ghrelin, peptide tyrosine tyrosine (PYY), glucagon-like peptide -1 (GLP-1), and cholecystokinin (CCK), in their total and/or active form. Standardised mean differences (SMD) were extracted as the effect size. RESULTS: 127 studies were identified: 19 RCTs, 108 non-RCTs, 1305 and 4725 participants, respectively. In response to weight loss induced by CR, EX or CREX, the meta-analysis revealed an increase in total ghrelin from both RCTs (SMD: 0.55, 95% CI: 0.07-1.04) and non-RCTs (SMD: 0.24, 95% CI: 0.14-0.35). A decrease in acylated ghrelin was identified for RCTs (SMD: -0.58, 95% CI: -1.09 to -0.06) but an increase was observed for non-RCTs (SMD: 0.15, 95% CI: 0.03 to 0.27). Findings also revealed a decrease in PYY (total PYY: SMD: -0.17, 95%CI: -0.28 to -0.06
PYY CONCLUSIONS: Weight loss induced by CR, EX, or CREX elicits an increase in total ghrelin, but varied responses in other appetite-related hormones. The extent of weight loss influences changes in appetite-related gut hormone concentrations.