Climb a Mountain on Snacks
How much food does it take to haul yourself up a mountain? Lifting your weight takes surprisingly little energy — but your muscles are only about 20% efficient, and you keep burning energy just being alive.
Lifting Yourself Is Cheap
Raising 90 kg by 3 500 metres takes about 3.1 MJ of work — only 740 kcal, the energy of three chocolate bars. But muscles waste about four fifths of their fuel as heat, so the food bill for the climbing itself is five times larger.
On a long expedition the biggest cost is simply living: a week on the mountain burns more energy at rest than all the climbing. At high altitude climbers often cannot eat enough and lose several kilograms of body fat.
Where the Food Energy Goes
kcalKey Relations
The potential energy gained by climbing; 1 kcal = 4184 J.
Muscles convert only a fraction η (about 20–25%) of food energy into mechanical work.
Add the resting energy for the days on the mountain. Real expeditions need even more: walking on the flat, carrying loads down, keeping warm.
Sources & Verification
- D. Halliday, R. Resnick & J. Walker, Fundamentals of Physics, 10th ed., Wiley, 2014 — Ch. 7 (Kinetic Energy and Work) and Ch. 8 (Potential Energy and Conservation of Energy).