The primary goal of the bodybuilder during the preparation for competition is to reduce subcutaneous fat through energy restriction. The body fat percentage of the subjects decreased from 9.6% to 6.5%, with the lowest individual value being 4.8 %. This is somewhat higher than has been reported in the literature before. However, the methodology of the determination of body fat percentage was also different between the studies. In our study the body fat percentage was measured using the DXA method, whereas previous studies have used the skinfold method and densitometry (3,4) or female subjects (23). A study by Karila et al (10) showed that DXA can be used to monitor body composition changes in relatively lean athletes. Nevertheless, those values together with very high muscle mass are one of the lowest found in the literature and provide excellent conditions to study the organism in the conditions of high constant negative energy balance. The negative energy balance of ERG group was about 200 kcal/day at T1 and reached about 950 kcal/day at T3 3 days before the competitions.
IGF-1 plays an important role in the regulation of somatic growth; metabolism; and cellular proliferation, differentiation, and survival (11) and is responsible for most, but not all, of the anabolic and growth-promoting effects of GH (6). Furthermore, reduced circulating IGF-I levels may indicate negative energy balance, which may lead to attenuated somatic growth (18). Moreover, Nemet et al (14) showed that exercise training can lead to a decrease in IGF-I in weight-stable subjects. IGF-I may also play a compensatory role to facilitate an appropriate anabolic response after resistance exercise in moderately hypoinsulinemic rats (7). However, during the conditions of severe hypoinsulinemia, IGF-I was not significantly different as a result of exercise (8). Therefore, low insulin concentration may hinder the compensatory role of IGF-I. This can be somewhat supported by the significant correlation between the change in insulin and IGF-I concentration found in our study (Figure 3).
Testosterone was decreased slightly but significantly after 5 weeks of energy restriction in ERG at T2 (from 20.3 ± 6.0 to 18.0 ± 6.8 ng/mL) and remained at the same level at T3. In general, weight reduction causes a decrease in plasma testosterone concentration with a very dramatic decrease under rapid weight reduction (10). Decreased testosterone levels were found in wrestlers (18) and judokas (5), which was accompanied by weight loss. These decreases are probably caused by dehydration combined with high-intensity training (5,10,21). However, training of bodybuilders was mainly aerobic, which may have a positive impact on testosterone concentration (12); therefore, after an initial decrease of testosterone at T2 it was possibly maintained by trainings.
It has been reported that bodybuilders must consume a relatively high-protein and low-fat diet (19) to prevent the loss of muscle mass. Amino acid supplementation augments recovery by mechanisms that are unclear but appear to involve increasing protein synthesis and/or reducing protein degradation and reducing muscle damage (17). The protein intake in ERG was about 2.5-2.6 g/kg during the study, which is similar to some previous literature concerning bodybuilders (3,19) and wrestlers (18) and is considered high compared to regular protein needs (1.0-1.2 g/kg) or for athletes (1.8-2.0 g/kg). Efficient recovery protein metabolism is critical to maintaining and promoting the anabolic processes involved in maintenance and development of skeletal muscle mass (1). In our study, however, we found a positive correlation between changes in insulin and IGF-I concentrations and lean body mass. This might indicate the importance of maintaining the concentrations of key anabolic hormones to prevent the loss of muscle mass. On the other side, decreases in fat mass were also significantly related to decreases in insulin and IGF-I, which is actually the purpose in preparation for competition of a bodybuilder. In contrast, it is also known that amino acids (i.e., leucine) can affect anabolic signals unrelated to hormones. Moreover, it has also been found that at insulin concentrations below 5 μU/mL, exogenous amino acids stimulate muscle protein synthesis (9). However, there is evidence that in the absence of insulin, amino acids are able to signal their presence but the effects of insulin and amino acids are maximal in the conditions of high physiological insulin concentrations.
In conclusion, severe energy restriction to extremely low body energy reserves decreases significantly the concentrations of 3 anabolic pathways despite high protein intake.
This study was supported by the Estonian Science Foundation grant number 6671. The authors have no conflicts of interests.
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