Anabolic and Catabolic Hormones and Energy Balance of the Male Bodybuilders During the Preparation for the Competition : The Journal of Strength & Conditioning Research

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Anabolic and Catabolic Hormones and Energy Balance of the Male Bodybuilders During the Preparation for the Competition

Mäestu, Jarek1; Eliakim, Alon2; Jürimäe, Jaak1; Valter, Ivo3; Jürimäe, Toivo1

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Journal of Strength and Conditioning Research 24(4):p 1074-1081, April 2010. | DOI: 10.1519/JSC.0b013e3181cb6fd3
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Competitive bodybuilding is a sport in which performance depends on physical appearance and posing ability rather than physical performance. Most of the year bodybuilders spend in the hypertrophy phase, where the aim is to gain and to increase the muscle mass. During the special preparatory period before the competitions bodybuilders aim to reduce their subcutaneous body fat to its minimum to enhance muscular definition. This can be obtained by negative energy balance in the body through restricting the energy intake and increasing energy expenditure. Despite efforts to maintain muscle mass during the preparatory period for competitions, if body energy reserves are limited, bodybuilders may loose muscle mass.

Limited published scientific research is available on bodybuilders during their final preparation to competition. Previous studies in the literature have monitored the diets of a bodybuilder before competitions and showed a significant decrease in body weight and body fat mass and a significant decrease of fat-free mass during the final 3 weeks of the 12-week study period (15). Body composition changes have also been investigated in female bodybuilders (23) and in male bodybuilders (3). However, to the best of our knowledge, no studies have investigated the energy expenditure of a bodybuilder during the preparation for the competition. This would allow the calculation of the energy balance and the anabolic-catabolic hormonal balance, which are critical for maintenance muscle mass during a severe weight-restriction period. It is known from the literature that insulinlike growth factor-1 (IGF-1) and insulin decrease in negative energy balance (18). The behavior of testosterone is not so clear, but in general it decreases (10). However, there is limited knowledge in the literature available to what extent those markers can decrease if negative energy balance is accompanied by limited body fat reserves.

The aim of this study was to determine the simultaneous effect of caloric intake, energy expenditure, and the biochemical parameters that affect the anabolic-catabolic balance in male bodybuilders during their preparation for a target competition. We hypothesized that severe energy restriction and negative energy balance prior to the competition will be associated with a significant decrease in anabolic hormones. Such a decrease may attenuate the ability of bodybuilders to maintain their muscle mass.


Experimental Approach to the Problem

Minimizing subcutaneous fat content and maintaining the muscle mass are important for bodybuilders before competition. To investigate the effect of energy balance on body composition and anabolic-catabolic hormonal profile, 2 groups of competitive bodybuilders, an energy-restricted group (ERG) and a control group (CG), were used to investigate the energy balance, body composition, and biochemical parameters during the final 11 weeks before competition to achieve negative energy balance. In CG energy intake and training volume were kept unchanged. Body composition was determined by dual-energy X-ray absorptiometry (DXA). Energy intake was determined using a 3-day eating diary (week and weekend days). Energy expenditure was determined by reports of total training volume (resistance and aerobic). Hormonal measurements included circulating concentrations of the anabolic hormones growth hormone (GH), IGF-I, IGF binding protein-3 (IGFBP-3), insulin and, testosterone and the catabolic hormone cortisol.


Fourteen male national- and international-level amateur bodybuilders (age 25.4 ± 8.0 years, training experience 7.8 ± 8.7 years) took part in this investigation (Table 1). The subjects were divided into ERG (n = 7) or CG (n = 7). The subjects were not using any drugs or anabolic steroids during the study and during the previous 2 years period and they were free of any disease. The competitors were tested for drugs during recent years and also at the competition for which they were preparing and none of them failed. The study design, purpose, and possible risks were explained to the subjects and written informed consent was obtained from the subjects prior to the investigation. This study was approved by the Ethical Committee of the University of Tartu.

Table 1:
Descriptive data (X ± SD) of the subjects at the beginning of the study period.


The study period was 11 weeks with the national championships at the end of week 11. This competition was the main one for the inclusion criteria to the national team to perform at the European Championships. The ERG was preparing for the championships with the aim of decreasing their body fat content through negative energy balance to build a physique with high muscular definition. They restricted their energy intake and at the same time increased their energy expenditure in an individual way that has been proved as most successful for each subject. CG did not change their eating or training pattern. One subject from ERG was excluded from all the analyses because of his decision not to participate in the championships and to stop the weight reduction. All subjects were tested 3 times-at 11 weeks (T1), 5 weeks (T2), and 3 days (T3) before the championships. The testing procedures were identical during each testing.

Body mass was measured to the nearest 50 g with the medical balance scale (A&D Instruments, Ltd., Abingdon, UK), and the height was measured with the Martin metal anthropometer (GPM, Siber-Hegner, Switzerland) to the nearest 0.1 cm. Body composition was measured using DXA with the Lunar DPX-L total body scanner (Lunar Corporation, Madison, WI, USA) that uses a constant potential X-ray source of 76 kVp and a cerium filter that produces dual-energy peaks of 38 and 62 keV. Soft tissue mass is measured pixel by pixel as a beam of photons penetrating the subjects' body. The DXA procedure has been shown to have precision errors to less than 1.5% for fat mass and lean body mass (13). The device was operated in the medium scan mode (∼20 minutes). The calibration of the machine was done daily as suggested by the manufacturer. The subjects were measured while wearing underwear only with their arms at their sides.

The subjects had fasted for at least 10 hours when their fasting blood samples (10 mL) were obtained from the antecubital vein in the upright position at 7:30 to 8:00 am to avoid diurnal changes. The plasma was separated and frozen at −20°C for later analysis. Cortisol, testosterone, IGF-1, IGFBP-3, and growth hormone were analyzed in duplicate on IMMULITE 2000 (DPC, Los Angeles, CA, USA). The interassay and intraassay coefficents of variation were less than 5%. Insulin was determined by means of an immunoradiometric assay (ICN Micromedic System, Horsham, PA, USA) with an intraassay and interassay coefficient of variance of 4.5% and 12.2% at an insulin concentration of 6.6 mU/L, respectively. Glucose was measured by means of the hexokinase/glucose 6-phosphate-dehydrogenase method by using a commercial kit (Boehringer Mannheim, Germany).

During the week of each testing time subjects fulfilled the consecutive 3-day (Thursday, Friday, and Saturday) eating diaries, with the indications of all the consumed food and food supplements. The subjects were instructed on the details needed for accurate recording of the quantity and the characteristics of the food consumed. Based on the diaries the daily energy intake (kcal/day) was calculated as the average of the 3 days. The daily energy expenditure was calculated according to the method of Bouchard et al (4) with the intraclass correlation of 0.96 for mean energy expenditure over 3 days. The subjects also had to report their total training volume (min/week) and the amount of aerobic training and strength training. The daily energy balance was calculated as the difference between the caloric intake and energy expenditure.

Statistical Analyses

Means and SDs were determined. Friedman analyses of variance by ranks were used to examine changes because the data were not normally distributed. The Wilcoxon matched-pairs signed rank test was used where post hoc analysis was relevant. The Wilcoxon matched-pairs signed-ranks test was also used to assess the differences between the measured variables in bodybuilders and control groups. Kendall rank correlation coefficients were used to evaluate associations among different variables of interest. Examining the 2-tailed hypothesis at a power of 0.80, the number of subjects required to demonstrate a significant difference in dependent variables at p ≤ 0.05 was calculated to be at least 5. The level of significance was set at p ≤ 0.05.


Total training volume was significantly higher during each week of the study in ERG (Figure 1), with no significant difference in the amount of the total volume of strength training between the 2 groups. Strength training was about 53.5% at T1 and was reduced to about 39% by T3 with a concomitant increase in aerobic training in ERG, whereas in CG the amount of strength training was not changed and was in the range of 65% during the whole study period.

Figure 1:
The amount of total training volume in the energy-restricted group (ERG; n = 7) and in the control group (CG; n = 7).

Nutrient intake, energy expenditure, and energy intake data for the ERG and CG are presented in Table 2. No significant differences were seen in the consumed food components during the study period in both groups; however, a tendency to decrease intake of carbohydrates was found at T3 in the ERG compared to T1. Protein, carbohydrate, and lipid intakes were about 28%, 60%, and 12% of calories consumed in the ERG group during the entire study period, respectively. The respective values were 25%, 60%, and 15% in the CG group. The energy intake of the ERG decreased about 13% from T1 to T3; however, the decrease was not statistically significant. The energy expenditure of the ERG was significantly higher at T2 and T3. The intake of proteins tended to be higher in the ERG compared to CG (p = 0.073) at T1. No more significant differences were found in ERG and CG groups. The increases in energy expenditure and deceases in energy intake resulted in negative energy balance at about 978 kcal/day at T3 in ERG.

Table 2:
Nutrient intake, energy expenditure, and energy intake parameters during the 11-week weight-reduction study in the energy-restricted group (ERG) and in the control group (CG).

The body mass and the body fat percentage of the ERG were significantly decreased during the study period (from 82.9 ± 9.3 to 78.8 ± 8.4 kg and from 9.6 ± 2.3 to 6.5 ± 1.5%, respectively) (Figure 2), whereas no significant changes were observed in the CG. No significant changes were seen in the body mass index, lean body mass, bone mineral component, or lumbar bone values in either ERG or CG (data not shown).

Figure 2:
Changes in body mass and body fat percentage in the energy-restricted group (ERG) and in the control group (CG) group during the 11-week weight-reduction period. Numbers indicate significant differences (p < 0.05) from the pointed testing.

All hormonal parameters were in the normal range within the study for both groups. At the beginning of the study no significant differences between the biochemical parameters of the 2 groups were observed (Tables 3 and 4). However, there was a tendency (p < 0.1) for a decreased insulin concentration in ERG when compared to the CG. In ERG, IGF-1 and insulin decreased significantly during the 11-week weight-reduction period (p < 0.05). In T2 and T3 testosterone concentration was significantly decreased in ERG when compared to T1. No significant changes were observed in the CG except a significant increase in testosterone concentration from T2 to T3.

Table 3:
Changes in the biochemical parameters during the 11-week weight-reduction period in the energy-restricted group.
Table 4:
Changes in the biochemical parameters during the 11-week weight-reduction period in the control group.

There were significant correlations in the change of IGF-I concentration and the changes in insulin (Figure 3), fat mass, lean body mass, and body mass (r = 0.652-0.741; p < 0.05). Changes in insulin concentrations were significantly related to changes in fat mass and lean body mass (r = 0.630-0.725; p < 0.05) (Figure 4). Changes in IGFBP-3 were significantly related to changes to changes in IGF-I and lean body mass (r = 0.689 and r = 0.697, respectively; p < 0.05). No more significant correlations were found between the change in biochemical and anthropometric parameters of the bodybuilders.

Figure 3:
Correlations between changes in insulin and changes in insulinlike growth factor-1 (IGF-1) concentrations during the 11-week weight-reduction period.
Figure 4:
The effect of the change in fasting insulin concentration to the change in lean body mass during the 11-week weight-reduction period.


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.

Regulation of the protein anabolism in response to oral feeding involves both stimulation of protein synthesis and a suppression of protein breakdown. These changes are mediated by feeding-induced increases in plasma concentrations of both nutrients and hormones (2). For example, protein balance is influenced by stimulatory (testosterone, IGF-I, insulin) and inhibitory (cortisol) hormones (24). IGF-I and GH activate the protein kinase B (Akt) pathway to increase translational efficiency and protein synthesis, whereas cortisol opposes it (20). The main finding of this study was that anabolic processes were affected negatively, as indicated by the significantly decreased concentrations of insulin and IGF-I and those biochemical changes were significantly related to the changes in the body composition. No significant changes were observed in testosterone and cortisol by the end of the study period. However, testosterone was significantly decreased during the initial energy-restriction period. Furthermore, the values of insulin and IGF-I decreased under the healthy reference value at T3. Fedele et al (8) showed that there is a critical concentration of insulin below which rates of protein synthesis begin to decline in vivo and it is possible that a low but critical concentration of insulin must be available for anabolism after exercise. Furthermore, it has been shown in rats that decreasing the postprandial plasma insulin level below a postabsorptive level resulted in an impairment of protein synthesis compared with postabsorptive protein synthesis (2).

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.

Figure 5 presents the individual data of 2 competitors. Competitor A was able to decrease most of his body fat percentage, whereas competitor B reached the lowest body fat value. Both athletes showed chronically decreased IGF-I and insulin concentrations by the end of the study period. They lost 1.8 kg and 1.5 kg of lean body mass, respectively; with about 1 kg lean body mass loss from T2 to T1. However, both subjects study had relatively high protein intake (i.e., about 28% at the beginning of the study and about 32-33% at the end of the study), which is considered as typical to maintain muscle growth.

Figure 5:
Changes in insulin (mU/L) and insulinlike growth factor-1 (IGF-1) (μg/L) concentrations in 2 competitors of the energy-restricted group. Competitor A lost 7.4% of his initial weight (100.2 kg). His body fat percentage at each testing was 10.3%, 7.8%, and 6.4%, respectively. His lean body mass dropped from 87.2 to 85.1 kg. Competitor B lost 5.5% of his initial weight (78.9 kg). His body fat percentage at each testing was 7.4%, 6.4%, and 4.8%, respectively. His lean body mass dropped from 71.3 to 70 kg.

We speculate how an increased protein intake may lead to the loss of muscle mass in severe energy-restricted conditions. In such conditions, a body can not use carbohydrates for energy because their reserves are critical as indicated also by decreased blood glucose values. Body fat reserves are also close to the minimum amount that are needed for survival and can not be used. If we now increase the amount of proteins for additional energy, we force the human body to use proteins for energy and to become accustomed to those conditions. However, there is still severe energy deficiency prevalent in the organism and, as the body gets accustomed to relying on additional energy from proteins, the “available” proteins in muscles may be catabolized and the loss of muscle mass increases. The critical body fat percentage in such conditions might be around 7.0-7.5% from where both insulin and IGF-I decrease under healthy reference values (Figure 5). This mechanism, however, needs further research. Instead of increasing the protein intake in a severe energy deficit, carbohydrates may benefit (22) by helping overcome the energy deficit-induced muscle mass loss. Ingesting carbohydrates with essential amino acids after weight training increased muscle protein synthesis compared to placebo (16). Furthermore, it increased postexercise insulin concentration, which has an impact on anabolic processes.

In conclusion, severe energy restriction to extremely low body energy reserves decreases significantly the concentrations of 3 anabolic pathways despite high protein intake.

Practical Applications

Monitoring the key anabolic hormones can help a bodybuilder to avoid losses in muscle mass during energy-restricted phases before a competition. Very low IGF-I and insulin values will be followed by rapid loss of muscle mass; therefore, if competitions are more than 10 days away, there would be a significant loss of muscle mass. Consumption of more proteins for energy in these conditions is questionable because of the downregulation of anabolic pathways. Stimulating insulin secretion by ingestion of carbohydrates may be helpful because the effects amino acids are higher at high physiological insulin concentration.


This study was supported by the Estonian Science Foundation grant number 6671. The authors have no conflicts of interests.


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weight restriction; energy intake; energy expenditure; anabolism; muscle mass

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