Calorie-restricted weight loss reduces muscle mass. Thus, clinicians and fitness professionals recommend resistance exercise to preserve muscle mass during calorie-restricted weight loss. However, the endocrine response of anabolic hormones such as growth hormone (GH) and insulin-like growth factor 1 (IGF-1) to resistance exercise during caloric restriction has not been characterized. Participants (n = 7) consumed a controlled liquid diet during three 3-day conditions of caloric restriction (15 kcal · kg FFM-1) with post-exercise carbohydrate (CRC), caloric restriction (15 kcal · kg FFM-1) with post-exercise protein (CRP) and an energy balance control (40 kcal · kg FFM-1) with post-exercise carbohydrate (CON). Serial blood draws were taken following 5 sets of 5 repetitions of the barbell back squat exercise on Day 3 of each condition. In CRC and CRP, respectively, GH peaked at 2.6 ± 0.4 and 2.5 ± 0.9 times the peak concentrations observed during CON. Despite this, IGF-1 concentrations declined 18.3 ± 3.4 % in CRC and 27.2 ± 3.8 % in CRP, which was greater than the 7.6 ± 3.6 % decline in CON, over the subsequent 24 hours. There is considerable anabolic resistance in the endocrine response to a single bout of resistance exercise which persists in the presence of post-exercise whey protein supplementation. Alternative strategies to restore the sensitivity of IGF-1 to GH stimulation during caloric restriction need to be explored. These strategies will empower clinicians and fitness professionals to make specific recommendations which minimize the deleterious effects of weight loss.      «

Calorie-restricted weight loss reduces muscle mass. Thus, clinicians and fitness professionals recommend resistance exercise to preserve muscle mass during calorie-restricted weight loss. However, the endocrine response of anabolic hormones such as growth hormone (GH) and insulin-like growth factor 1 (IGF-1) to resistance exercise during caloric restriction has not been characterized. Participants (n = 7) consumed a controlled liquid diet during three 3-day conditions of caloric restriction (15...     »