Exercise improves body composition, physical fitness, and blood levels of C-peptide and IGF-1 in 11- to 12-year-old boys with obesity

Abstract

Introduction: Exercise is vital in preventing and treating obesity. Despite its importance, the understanding of how exercise influences childhood obesity at the biochemical level is limited. In this study, we explore the effects of a 16-week exercise program (EP) on body composition, physical fitness, and the blood levels of hormones related to obesity.

Methods: Sixteen boys with obesity (n = 16) and seventeen boys without obesity (n = 17) took part in an EP comprising sports games and aerobic and resistance exercises. We examined alterations in body composition and physical fitness. In addition, we measured circulating hormone levels, including C-peptide, resistin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH), in the blood.

Results: Body fat percentage (BFP) decreased from 37.61% at pre-EP to 29.16% at post-EP in the obese group, but not in the non-obese group. The EP decreased C-peptide (4.58 ng/mL vs. 2.96 ng/mL, p < 0.001) and resistin levels (14.05 ng/mL vs. 11.06 ng/mL, p < 0.001) in the obese group. After the EP, significant improvement in IGF-1 (non-obese: 265.56 ng/mL vs. 311.81 ng/mL, p < 0.001; obese: 224.74 ng/mL vs. 272.89 ng/mL, p < 0.001) and GH levels (non-obese: 3.91 ng/mL vs. 4.80 ng/mL, p < 0.05; obese: 1.76 ng/mL vs. 2.51 ng/mL, p < 0.05) were observed in both groups. Lower C-peptide levels were associated with BFP (r = 0.447, p = 0.009) and muscle mass (r = -0.385, p = 0.02), whereas enhanced IGF-1 levels correlated with increased muscle strength (r = 0.343, p = 0.05) and cardiovascular fitness (r = 0.347, p = 0.04). Multiple linear regression analysis revealed that cardiovascular fitness variability and BFP in the obese group were determined by C-peptide (β = -0.054, p < 0.001) and IGF-1 levels (β = -2.936, p < 0.05), respectively.

Discussion: Exercise may induce positive effects on improvements in body composition and physical fitness, as well as on blood levels of metabolic biochemicals such as C-peptide and IGF-1, in adolescent boys with obesity.

Keywords: C-peptide; IGF-1; childhood obesity; exercise; physical fitness.

FIGURE 1

Association of changes in body composition and physical fitness with C-peptide and IGF-1 levels after exercise intervention. (A, B) The change in (Δ) C-peptide levels was correlated with the change (Δ) in BFP (r = 0.447, p = 0.009) and muscle mass (r = −0.385, p = 0.026) after undergoing the EP in the non-obesity and obesity group. (C) The change in (Δ) C-peptide levels was correlated with the change (Δ) in cardiovascular fitness (r = −0.525, p = 0.036) after undergoing the EP in the obesity group. (D, E) The change (Δ) in IGF-1 levels was correlated with the change (Δ) in back-muscle strength (r = 0.343, p = 0.05) and cardiovascular fitness levels (r = 0.347, p = 0.047) after undergoing the EP in the non-obesity and obesity group. (F) The change in (Δ) IGF-1 levels was correlated with the change (Δ) in BFP (r = −0.542, p = 0.003) after undergoing the EP in the obesity group. A correlation analysis was performed (Pearson’s correlation coefficients). Each gray and back circle represents a participant in the non-obesity (n = 17) and obesity (n = 16) groups, respectively.