Effects of exercise training intensity on nocturnal growth hormone secretion in obese adults with the metabolic syndrome

Context: Abdominal adiposity is associated with reduced spontaneous GH secretion, and an increased incidence of the metabolic syndrome, type 2 diabetes, and cardiovascular disease. Exercise training increases GH secretion, induces abdominal visceral fat loss, and has been shown to improve the cardiometabolic risk factor profile. However, little is known about the effects of endurance training intensity on spontaneous GH release in obese individuals. Objective: Our objective was to examine the effects of 16 wk endurance training on spontaneous 12-h overnight GH secretion in adults with the metabolic syndrome. Design and Setting: This randomized, controlled exercise intervention was conducted at the University of Virginia. Participants: A total of 34 adults with the metabolic syndrome (mean ± SEM: age: 49.1 ± 1.8 yr) participated. Intervention: Participants were randomized to one of three groups for 16 wk: no exercise training (control), low-intensity exercise training, or high-intensity training. Main Outcome Measure: Change in nocturnal integrated GH area under the curve (AUC) was calculated. Results: Both exercise training conditions augmented within-group nocturnal GH AUC pretrain to post-training (low-intensity exercise training approximately ↑ 49%, P < 0.05; and high-intensity training approximately ↑ 65%, P < 0.01), and these changes were also greater than the changes in the control group (P < 0.01). The change in nocturnal GH AUC was inversely associated with the change in fat mass across the entire sample (r = -0.34; P = 0.051; n = 34) but was not significantly associated with the change in abdominal visceral fat (r = 0.02; P = 0.920; n = 34). Conclusions: Sixteen wk of supervised exercise training in adults with the metabolic syndrome increases spontaneous nocturnal GH secretion independent of exercise training intensity.