Participants
The study included 19 female elite soccer players who voluntarily participated and were divided into two groups: the “controlled-diet group” (CG) (n = 10; 19 ± 1.4 years; 63.6 ± 10 kg; 164 ± 2.0 cm) and the “exchange-diet group” (EG) (n = 9; 22.5 ± 4.8 years; 61.3 ± 7 kg; 164 ± 0.1 cm). A simple randomization was performed by generating a table of random numbers without repetition. Even numbers were assigned to the CG and odd numbers to the EG. All participants belonged to the same Spanish team and performed the same training program, which included 8 hours per week of practice and one official match per week. During the intervention players were not allowed to engage in any other training, to follow a different nutritional plan or to use any ergogenic aid that could affect the results. Prior to the start of the intervention, the players were fully informed about the purposes and risks of the study and provided written informed consent. They also completed a form with their personal, medical, and training details. The research project was conducted in accordance with the Declaration of Helsinki and was approved by the University Review Board for use of Human Subjects (Code: UEMC 10_2021) (