This article presents a mathematical model to calculate how much food to pack for your trip based on energy balance, energy-mile theory, and body fat utilization, and discusses some ways to respond to model factors in order to save food weight on the trail.

Dinnertime in the High Sierra - trout chowder.

Answering the question:

How much food do I bring on my backpacking trip?

requires some consideration of a basic energy balance equation we can write as:

Calories of Energy Expended = Calories of Food Eaten + Calories of Body Fat Consumed

Since Calories of Food Eaten is what we're really after, then we can rewrite the equation as:

Calories of Food Eaten = Calories of Energy Expended - Calories of Body Fat Consumed

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Of course, the usual disclaimer applies: physiology and metabolism are far more complex than this. This equation is merely one attempt to simplify the process and capture the major components of energetics so we can (as a starting point) estimate how much food to pack on a trip. This equation represents a highly reliable, time-tested approach that I've been using (and validating) for more than 30 years. Of course, YMMV.

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In fine ultralight style, assuming we want to exit at the trailhead with no excess food, we're hoping that

Calories of Food Packed - Calories of Food Eaten = 0

Thus, I'd like to have a reasonable answer to the two questions:

1. How many Calories of energy will I expend on my trek?
2. How many Calories of body fat will I consume on my trek?

The rest of this article focuses on answering these two questions, and how an understanding of these answers can allow us to save pack weight on food.

Learn More

Learn how this is practiced in a before-and-after case study for an actual trek, in the author's upcoming lightweight backpacking masterclass.