I think it's pretty obvious. I believe that it is not that exercise helps, but sedentarism is poisonous. A sedentary 40 year old looks and feels 20 years older than a 40 year old athlete.
Yes, how about taking pictures of a bunch of 40 year old marathon runners and putting it next to a picture showing a bunch of 20 year old overweight accountants and then ask people to guess the average age of each group? That should be pretty simple and covers at least the "looks" claim.
actually a 40yr old athlete that has already more than 20 year of athlete life behind will have a body in a much more bad shape than a guy who had regular walks and healthy diet.
