The issue with RCTs is that you can only run them under tight conditions for so long on humans, so it's difficult to measure long-term outcomes like lifespan.

The issue with RCTs is that you can only run them under tight conditions for so long on humans, so it's difficult to measure long-term outcomes like lifespan. (Not to disagree with you on exercise. All data seems to point towards exercise being the first lever people should look to pull---as opposed to nutrition issues that people will have endless debates about---in terms of improving health.)