Which research question would most directly address the uncertainty that high protein intake may displace other important nutrients at the population level?

Do all proteins from animal sources provide identical amino acid profiles and health effects without considering total caloric context, as determined by theoretical nutrient composition tables only?

Does a long-term diet that provides protein at 40% of calories, compared with one at 20% while holding total energy constant, lead to measurable reductions in dietary fiber, calcium, and certain micronutrients and corresponding negative health outcomes over 3 years in healthy adults?

Are people who prefer meat-based diets more likely to exercise, based solely on a one-time questionnaire about food likes and gym membership?

Does acute ingestion of a high-protein meal increase immediate satiety compared with a high-sugar beverage, as measured by subjective appetite ratings over 2 hours?