title: Obesity attenuates the growth hormone response to exercise.
abstract: Resting serum GH concentrations are decreased in obesity. In nonobese (NonOb) individuals, acute exercise of sufficient intensity increases GH levels; however, conflicting data exist concerning the GH response to exercise in obese individuals. To examine the exercise-induced GH response in obese individuals, we studied 8 NonOb, 11 lower body obese (LBO), and 12 upper body obese (UBO) women before, during, and after 30 min (0800-0830 h) of treadmill exercise at 70% oxygen consumption peak. Blood samples were taken every 5 min (0700-1300 h) and were analyzed for GH concentrations with a sensitive (0.002 microg/L) chemiluminescence assay. The impact of 16 weeks of aerobic exercise training on the GH response to exercise was also examined in the obese women. In response to exercise, the 6-h integrated GH concentration was significantly greater (P < 0.05) in the NonOb women (1006 +/- 220 min/microg x L) than in either of the obese groups (LBO, 435 +/- 136; UBO, 189 +/- 26 min/microg x L). No differences were found between the LBO and UBO women. The increased integrated GH concentrations could be accounted for by a greater 6-h GH production rate [micrograms per L distribution volume (Lv)] in the NonOb women than in either of the obese groups (NonOb, 45.6 +/- 12.3; LBO, 16.9 +/- 1.2; UBO, 8.7 +/- 0.64 microg/Lv; P < 0.05). This increase was attributed to a greater mass of GH secreted per pulse in the NonOb women (NonOb, 10.8 +/- 2.5; LBO, 4.9 +/- 0.8; UBO, 4.0 +/- 0.5 microg/Lv; P < 0.05, NonOb vs. both obese groups). After 16 weeks of aerobic training, maximal oxygen consumption increased from 44.7 +/- 2.2 to 48.5 +/- 1.9 mL/kg fat-free mass x min; P < 0.05), but no significant change in body composition occurred in the 10 obese women who completed the training. No change was observed in the GH response to exercise after training (n = 10; pre, 379 +/- 144; post, 350 +/- 55 min/microg x L). In conclusion, the GH response to exercise was attenuated in the obese women compared to NonOb women. Short term aerobic training improved fitness, but did not increase the GH response to exercise.
authors.affiliation: Department of Exercise Science, Syracuse University, New York 13244, USA. jakanale@sued.syr.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Kanaley
authors.forename: M M
authors.initials: MM
authors.lastname: Weatherup-Dentes
authors.forename: E B
authors.initials: EB
authors.lastname: Jaynes
authors.forename: M L
authors.initials: ML
authors.lastname: Hartman
mesh_terms: D001823:Body Composition; D001824:Body Constitution; D015992:Body Mass Index; D015444:Exercise / Q000502:physiology*; D005260:Female; D019382:Human Growth Hormone / Q000097:blood* / Q000378:metabolism; D006801:Humans; D009765:Obesity / Q000503:physiopathology*; D010101:Oxygen Consumption
chemical_list: D019382:Human Growth Hormone