ISSA Nutritionist Practice Exam

Protein catabolism is most likely to occur during which of the following activities?

1. A 2 hour swim

2. A short sprint

3. During sleep

4. After binge eating

The correct answer is: A 2 hour swim

Protein catabolism, the process by which proteins are broken down into amino acids for energy, is most likely to occur during prolonged or intense physical activity when the body's energy reserves are depleted. During a long-duration activity such as a two-hour swim, the body may exhaust its glycogen stores (which derive from carbohydrates) and begin to break down proteins for energy, particularly if the swim is at a moderate intensity and extends beyond the duration in which glycogen can supply sufficient energy. In contrast, a short sprint typically relies heavily on anaerobic energy systems that primarily utilize carbohydrates, so protein catabolism would not be a significant factor during such a quick burst of activity. During sleep, the body is primarily in a state of repair and recovery, where muscle synthesis tends to prevail over breakdown. After binge eating, the body is more likely focused on processing the influx of nutrients rather than catabolizing proteins for energy, as there is an abundance available from recent food intake. Thus, a prolonged endurance activity like a two-hour swim is when the body is most likely to start utilizing protein as an energy source, making it the most suitable answer for this question.