Nigeria, Feb. 2 -- My recent article, "Obesity Is Stalled Flow and Not a Failure of Willpower," generated thoughtful responses from readers asking what "flow" really means and how metabolic health can be understood beyond diets and the latest longevity buzzwords that have gained attention since COVID-19. The short answer is that walking is the main lever for metabolic health and not because it burns calories, but because it keeps energy moving through an open biological system.

I grew up in a village where lizards often lay still in the sun, and snakes could sometimes be seen stretched across the road on the way to the farm, seemingly "bathing" in the warmth. These are so-called ectothermic animals whose metabolism depends on external h...