Obesity attenuates the growth hormone response to exercise

Resting serum GH concentrations are decreased in obesity. In nonobese (NonO b) 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 ind ividuals, we studied 8 NonOb, II lower body obese (LBO), and 12 upper body obese (UBO) women before, during, and after 30 min (0800-0830 h) of treadmi ll 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 mu g/L) chemiluminescence assay. The impact of 16 weeks of aerobic exercise training on the GH response to exercise was also examined in the o bese women. In response to exercise, the 6-h integrated GN concentration wa s significantly greater (P < 0.05) in the NonOb women (1006 +/- 220 min/mu g.L) than in either of the obese groups (LBO, 435 +/- 136; UBO, 189 +/- 26 min/mu g.L). No differences were found between the LBO and UBO women. The i ncreased into-grated GH concentrations could be accounted for by a greater 6-h GH production rate [micrograms per L distribution volume (L-v)] 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 mu g/L-V; P < 0.05). This increase was attr ibuted 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 mu g/L-V; P < 0.05, NonOb us. 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 mas s.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 t he GH response to exercise after training (n = 10; pre, 379 +/- 144; post, 350 +/-: 55 min/mu g.L). In conclusion, the GH response to exercise was att enuated in the obese women compared to NonOb women. Short term aerobic trai ning im proved fitness, but did not increase the GH response to exercise.