I cut 2kg from my gear and then carried 4kg of food for five days — how many grams a day actually works?

On the leftovers, which is the more interesting half of your question.

Coming home with a day and a half is extremely common and it has two causes that need different fixes:

Appetite lags effort. For the first couple of days a lot of people eat noticeably less than they planned, and hunger arrives properly around day three. So a flat rate per day over-supplies the start. Packing lighter for days one and two and heavier for the back half matches this and saves real weight.

Packing meals rather than weight. A meal is an unbounded unit and it is always generous. Weighing turns it into a number you can decide about.

The structural fix, though, is not in the packing at all: plan around resupply. Carrying five days of food is a choice, and on most routes it is avoidable. Half a day off-trail to a shop removes two kilos from your back for the harder half of the walk, and the time cost is usually less than the time cost of walking slower under the weight.

When there genuinely is no resupply, then the density arithmetic above is the lever, and being deliberate about days one and two is the rest of it.

One thing worth doing after every trip while it is fresh: write down what you had left and what you were sick of. Two trips of that and your list becomes accurate in a way no general advice can be, because appetite on trail is quite personal.

The two numbers connect through one figure, and once you use it the planning becomes arithmetic instead of guesswork: calories per gram.

Decide the calories you want per day, then divide by the calorie density of your food to get the weight. That is the whole method, and it explains why two people carrying the same calories can be two kilos apart.

Rough densities worth knowing:

• Fats and nuts, around 6 to 9 calories per gram — the densest thing you can carry
• Dry carbohydrates, around 3.5 to 4 — pasta, couscous, oats, most bars
• Dehydrated meals, often 4 to 5, sometimes less than people assume once you read the packet
• Anything with water in it, well under 2 — this is where the weight goes

A useful target is around 4 calories per gram overall. Below 3.5 and you are carrying water and packaging. Above 5 is achievable but the food tends to be relentless to eat.

So at, say, 3000 calories a day at 4 per gram, that is 750g a day. Five days is under 4kg — which is roughly what you carried, so your problem is probably not the density, it is the quantity and the leftovers.

The practical step: weigh everything once, and write the weight and calories on a list you reuse. Half an hour, and every future trip is a calculation.