What percentage of body weight loss is associated with thirst?

• A. 2% of body weight
• B. 5-10% of body weight
• C. 10-15% of body weight
• D. 15% or more of body weight

Answer: (A)

Thirst signals begin when the body's water deficit becomes noticeable, which is typically around 2% of body weight. As you sweat, you lose water and your weight drops; reaching about a 2% loss triggers your body's thirst mechanism to prompt drinking. For example, a person who weighs 70 kg would experience thirst around a 1.4 kg (about 1.4 liters) fluid loss. This early cue is why keeping up with fluids before you feel dry is important. Larger dehydration levels—around 5-10% or more—produce more obvious performance declines and greater risk of heat-related issues, which is why those higher losses are associated with more severe effects rather than the initial thirst signal.