School grades, food grades, health grades, trail grades…elevation profiles and the speed at which they are traversed are caloric profiles.
The precise relationship between how fast you walk, how steep your trail is, and how much energy you burn turns out to be less obvious than you might assume, which is why researchers at the United States Army Research Institute of Environmental Medicine decided to develop an equation that captures these nuances.” how-many-calories-burned-hiking
I would think the intensity of aerobic respiration would tell the story, but it is not so simple. At any rate, or grade, resting intervals with softer or nearly flat portions on trails is a key design feature for a more enjoyable experience in my opinion.
Related, “Protein restriction is much less difficult to maintain than dietary restriction, and it may even be more powerful because it suppresses both TOR and IGF-1, the two pathways thought responsible for the dramatic longevity and health benefits of caloric restriction…the proportion of protein intake was more important for life extension than the degree of caloric restriction” living-longer-by-reducing-leucine-intake