Why do only high-performance athletes typically require carbohydrate and protein intakes above general dietary guidelines?

• A. Because their repeated high-intensity training requires much larger glycogen stores and greater muscle repair and synthesis demands compared with typical daily activity levels.
• B. Because general guidelines are intentionally set low to discourage all physical activity unless athletes train professionally, and only athletes are permitted to exceed them for performance reasons.
• C. Because non-athletes cannot metabolize the extra carbohydrate and protein efficiently, so extra intake would be wasted regardless of exercise level.
• D. Because high-performance athletes have chronically lower resting metabolic rates which force them to increase intake of carbs and proteins to maintain body weight.

Answer: (A)