Growth Hormone Administration Conserves Lean Body Mass during Dietary Restriction in Obese Subjects*

Abstract

Because weight-reducing diets result in loss of lean body tissue as well as fat, we sought to determine whether injections of. GH might facilitate the preservation of nitrogen and accelerate the loss of body fat during dietary restriction. The dietary intake of 8 obese subjects was restricted to 24 Cal/ kg ideal BW and 1 g protein/kg for 11 weeks. During weeks 3– 5,4 subjects were given a total of 10 im injections of recombinant methionyl human GH, 1 morning injection every 48 h in a dosage of 0.1 mg/kg ideal BW. The other 4 subjects were given injections of vehicle. During weeks 8–10, the subjects who had received GH previously were given vehicle and vice versa. While receiving GH injections the mean daily nitrogen deficit [0.35 ± 2.14 (±SD) g/day] was significantly less than the loss during injection of vehicle (2.21 ± 1.45 g/day; P < 0.001). Although three of sixsubjects lost 190% more fat (as determined by hydrostatic weighing) while receiving GH,the difference in group mean fat loss during GH injection was not significantly greater than that during injection of vehicle (3.06 ± 1.39 kg lost with GH vs. 2.64 ± 1.08 kg lost with vehicle; P = NS). In parallelwith the changes in nitrogen balance, GH produced a significant increase in the mean plasma somatomedin-C/insulin-like growth factor I concentration. From a mean pretreatment value of 1.06 ± 0.28 U/mL, a maximal value of 3.20 ± 1.60 U/mL was achieved after 12 days of GH injection (P < 0.001). Somatomedin-C/ insulin-like growth factor I concentrations did not change during injection of vehicle. During GH injection weight loss was attenuated because of fluid retention. If weight loss was determined 1 week after the end of GH administration, however, the total weight loss (3.42 ± 1.73 kg) was not significantly different from that during the 3 weeks of vehicle administration and the following week (4.16 ± 1.30 kg). Fasting blood glucose and serum insulin concentrations did not change during GH administration, and no glycosuria was detected in morning urine samples. Short term GH administration is effective in decreasing the loss of lean body mass in individuals ingesting restricted diets. However, fat loss was not accelerated.