An athlete who has increased intake of chicken, tuna, and beef but reports decreased energy may likely be experiencing:

The athlete's increased intake of chicken, tuna, and beef indicates a likely boost in protein consumption, which is essential for muscle repair and growth, especially in athletes. However, the report of decreased energy suggests that the athlete's carbohydrate intake may be insufficient.

Carbohydrates serve as a primary energy source for high-intensity exercise and physical activity. When an athlete does not consume enough carbohydrates, this can lead to reduced glycogen stores, resulting in fatigue and decreased performance. Therefore, while the athlete may be meeting protein needs, if they are not adequately fueling with carbohydrates, they could experience low energy levels. This underscores the importance of a balanced diet that includes sufficient carbohydrates alongside protein to support overall energy demands in athletic training and competition.