What’s a runner gotta do? ∞
Here’s a short, fascinating ultra-running case study with a counter-intuitive outcome: Philippe Fuchs ran from Paris to Beijing, covering ~5,100 miles in 161 days. He “lost five pounds during the run, and his percent body fat dropped from 21.5% to 16.5%. You’d think this would make him more oxygen efficient. It didn’t.” Damn! Biology is wacky.