Calorie Restriction and Matched Weight Loss From Exercise: Independent and Additive Effects on Glucoregulation and the Incretin System in Overweight Women and Men

Abstract

Objective: It is not known whether calorie restriction (CR) has additive benefits to those from exercise (EX)-induced weight loss. We hypothesized that weight loss from CR and EX (CREX) improves insulin sensitivity more than matched weight loss induced by EX or CR alone and that the incretin system may be involved in adaptations to CR.

Research design and methods: Sedentary, overweight men and women (n = 52, 45-65 years of age) were randomized to undergo 6-8% weight loss by using CR, EX, or CREX. Glucose, insulin, C-peptide, insulin sensitivity, and incretin hormones (glucagon-like peptide 1 [GLP-1] and glucose-dependent insulinotropic polypeptide [GIP]) were measured during frequently sampled oral glucose tolerance tests (FSOGTTs). Incretin effects on insulin secretion were measured by comparing insulin secretion rates from the FSOGTTs to those from a glycemia-matched glucose infusion.

Results: Despite similar weight losses in all groups, insulin sensitivity index values increased twofold more in the CREX group (2.09 ± 0.35 μM/kg/pM × 100) than in the CR (0.89 ± 0.39 μM/kg/pM × 100) and EX (1.04 ± 0.39 μM/kg/pM × 100) groups. Postprandial GLP-1 concentrations decreased only in the CR group (P = 0.04); GIP concentrations decreased in all groups. Incretin effects on insulin secretion were unchanged.

Conclusions: CR and EX have additive beneficial effects on glucoregulation. Furthermore, the adaptations to CR may involve reductions in postprandial GLP-1 concentrations. These findings underscore the importance of promoting both CR and EX for optimal health. However, because data from participants who withdrew from the study and from those who did not adhere to the intervention were excluded, the results may be limited to individuals who are capable of adhering to a healthy lifestyle intervention.

Trial registration: ClinicalTrials.gov NCT00777621.

Figure 1

Body weight and composition changes (top panel) and measures of intervention compliance (bottom panel). Values are reported as the least squares mean ± SE from ANCOVAs in which the change in the outcome was the dependent variable, study group was the independent variable, and baseline values were the covariate. P values reflect the significance of the overall ANCOVA. When overall ANCOVAs were significant at P ≤ 0.05, post hoc paired comparisons were performed according to the principle of protected F tests and least significant difference tests. *P ≤ 0.05 vs. zero (significance of within-group change). †P ≤ 0.05 vs. CR group. ‡P ≤ 0.05 vs. CREX group.