###### Abstract  
This case study aimed to evaluate the body composition and several biochemical markers during a 7-month pre-competition training period of a natural male bodybuilder. The athlete monitored his nutrition, training variables, and daily physical activity during the preparation phase. At the beginning (W31), in the middle (W18), and one week before the contest (W1), measurements included body composition via DEXA, testosterone and cortisol hormonal concentrations, and lipid, blood, and liver biochemical markers via an automated hematology analyzer. A gradual decrease in energy intake (\(-27.6\%\)) and increased daily activity (\(169.0\%\)) was found. Fat mass decreased from \(17.9\) kg (W31) to \(13.1\) kg (W18) and \(4.2\) kg (W1), while lean body mass decreased from \(69.9\) kg (W31) to \(68.2\) kg (W18) and \(66.7\) kg (W1). Bone density decreased linearly, and bone mass decreased from W31 to W1 by \(1.7\%\). Testosterone decreased from \(5.4\) ng\(\cdot\)mL\({}^{-1}\) (W31) to \(5.3\) ng\(\cdot\)mL\({}^{-1}\) (W18) and \(4.4\) ng\(\cdot\)mL\({}^{-1}\) (W1), while cortisol increased from \(21.3\) ug\(\cdot\)dL\({}^{-1}\) (W31) to \(20.3\) ug\(\cdot\)dL\({}^{-1}\) (W18) and \(24.4\) ug\(\cdot\)dL\({}^{-1}\) (W1). In conclusion, a slow rate of weight loss and training with repetitions nearly to failure, combined with weekly monitoring of training and nutrition, may significantly improve to maintain their muscle mass with the greatest possible reduction in body fat by utilizing a hypocaloric diet [4; 5]. However, extreme diets and training methods may lead to potential health risks [6; 7]. In the physique category, muscle mass is an important factor for success. Therefore, athletes follow long-term diets with a relatively reduced rate of fat loss to retain muscle mass [2]. Before the hypocaloric period, athletes follow a long period of energy surplus designed to increase muscle mass and minimize adipose tissue growth [5]. During this period (off-season), athletes increase their energy intake mainly by increasing their carbohydrate intake, which is the primary fuel of training. The following training phase is the 'pre-competition period', commonly known as \"preparation\", which is characterized by a caloric deficit and aims to reduce body fat with maximum preservation of muscle mass [3; 5]. Previous case studies of male bodybuilding athletes showed a substantial reduction in carbohydrate intake during the contest preparation phase, followed by an increase in protein intake [3; 8; 9]. Additionally, this hypocaloric period led to a reduction in body mass (approximately 14.0 kg-15.3 kg), which in turn translated to a substantial decrease in body fat (approximately 6.8-10.2%) and a reduction in muscle mass (approximately 3 kg-7 kg) [3; 8; 9]. Although these studies followed different diet methods, there is an agreement that during the contest preparation phase, a hypocaloric diet leads to a significant loss in muscle mass. Moreover, bone mineral content appeared to be increased following 26 weeks of preparation training for a contest (from 3.17 to 3.31 kg), with a concomitant increase in bone mineral density (from 1.35 to 1.42 g\(\cdot\)cm\({}^{-3}\)) in an amateur bodybuilder [8]. However, this result is in contrast to the typical outcome observed during hypocaloric training periods [10; 11]. Therefore, more studies on natural bodybuilders are required to reach safe conclusions regarding the changes in body composition and physical condition following a bodybuilding contest preparation phase. During the preparation phase prior to a contest, significant alternations occur in hormones. For example, testosterone may be negatively affected [9; 12; 13], while on the contrary, cortisol may increase [14]. A case study of a male natural professional bodybuilder showed that testosterone reduced during a 6-month preparation phase, reaching lower reference values (from 9.22 to 2.27 ng\(\cdot\)mL\({}^{-1}\)), while cortisol increased (from 10.52 to 21.07 ug\(\cdot\)dL\({}^{-1}\)) [9].