Final answer:
An Olympic athlete with mild dehydration is likely to experience increased thirst and may also have headaches or dizziness. Thirst is an early and primary indicator of the need to rehydrate.
Step-by-step explanation:
An Olympic athlete experiencing mild dehydration is likely to show symptoms such as increased thirst, slight headaches, and possibly dizziness or lightheadedness. Thirst is a primary indicator of dehydration and one of the body's first signals to increase water intake. While loss of appetite can be associated with dehydration, it is typically a more advanced symptom and might not be as immediately apparent as the early signs like thirst and headache. Mild dehydration can occur from inadequate water consumption during prolonged physical activity, especially in hot environments which lead to excessive sweating and greater water needs.