Caloric planning for mountain hiking sits at the intersection of physiology, logistics and experience. Get it right and the food is adequate, the pack is not unnecessarily heavy, and you arrive at the end of each day with enough fuel left to function properly and recover. Get it wrong — which most hikers do, in the direction of under-planning — and the latter hours of demanding days involve a progressive cognitive and physical decline that feels like tiredness but is actually a fuel deficit.

The Caloric Expenditure Calculation

Mountain hiking caloric expenditure depends on four variables: body weight, pace, terrain and pack weight. The standard formula for an approximation:

Calories per hour = (body weight in kg × 3.5 × MET value) / 200 × 60

Where MET (Metabolic Equivalent of Task) values for hiking:

For practical planning: a 70kg hiker on a demanding 7-hour alpine day burns approximately 500–600 calories per hour of active hiking = 3,500–4,200 calories from exercise alone. Add the basal metabolic rate (approximately 1,800 calories for a 70kg adult at rest) and the total daily energy expenditure is 5,300–6,000 calories.

The Deficit Problem: Why Under-Fuelling Is So Common

Most hikers carry food that provides 2,000–2,500 calories for a 7-hour alpine day that requires 3,500–4,200 calories. This 1,000–2,200 calorie deficit is the rule, not the exception. The reasons:

• Appetite suppression at altitude and during effort: high-intensity aerobic exercise suppresses appetite; hikers genuinely don’t feel hungry at the caloric demand rate and underestimate the deficit
• Day-hike food habits carried to demanding terrain: a 2-hour forest walk needs a lunch and some snacks; an 8-hour alpine day needs significantly more, and the habits built on shorter walks don’t automatically scale
• Pack weight optimisation without caloric optimisation: reducing pack weight by reducing food is the wrong trade-off — a lighter pack with inadequate food produces a faster hiker for three hours followed by a significantly impaired one for the remaining five

The consequences of caloric deficit on the mountain

A moderate caloric deficit (500–1,000 calories below requirement) produces: increased perceived effort on the same terrain, reduced cognitive function (slower navigation decisions, poorer risk assessment), increased fatigue earlier in the day, and significantly worse recovery overnight. A severe caloric deficit (1,500+ calories below requirement) on a consecutive-day multi-day trek produces what hikers describe as “hitting the wall” — the abrupt performance collapse of glycogen depletion that can be dangerous on technical terrain.

The Planning System: From Calculation to Pack Weight

Step 1: Calculate daily caloric requirement

Using the formula or shorthand above, calculate the caloric expenditure for the planned day including: distance, elevation gain/loss, terrain type, estimated pace and group weight.

Step 2: Select food by caloric density

Target 500–600 calories per 100g of food carried. Foods at this density: nuts (600 cal/100g), dark chocolate (550 cal/100g), hard cheese (400–450 cal/100g), nut butter (590 cal/100g), salami (400–500 cal/100g), freeze-dried meals (430–500 cal/100g). Foods below this density: fresh fruit (50–90 cal/100g), sandwiches (200–250 cal/100g), crackers alone (350–380 cal/100g).

Step 3: Calculate required food weight

Divide the caloric requirement by the caloric density of the planned food mix. At 500 cal/100g average density:

• 3,000 calorie day → 600g of food
• 3,500 calorie day → 700g of food
• 4,500 calorie day → 900g of food

Step 4: Add the 10–15% emergency reserve

Every food plan should include a 10–15% caloric reserve — food that is not expected to be consumed but is available if the day goes longer than planned. This reserve is carried in a clearly labelled separate section of the pack and is not touched unless needed.

Caloric Planning for Multi-Day Treks

Multi-day trek food planning differs from day hike planning in one critical respect: the cumulative caloric deficit. A 500-calorie daily deficit that is manageable on day one compounds to a 3,500-calorie deficit by day seven — the equivalent of a full day’s fuel missing from the system. The performance collapse that many hikers experience on days 4–5 of a multi-day trek is this accumulated deficit manifesting.

The multi-day planning rule: increase daily food provision by 10% per day beyond day three, reflecting the increasing physiological demand of consecutive high-output days. A day-one food provision of 600g should be 660g by day four and 720g by day seven — not the same provision repeated uniformly across all days.