Why the right snack changes the whole day

Ask most walkers what's in their rucksack and they'll talk happily about boots, waterproofs and the route card. Ask about food and you'll often get a shrug and a packet of crisps. That's a shame, because on any walk longer than a couple of hours — and especially on anything with real climbing in it — what you eat matters almost as much as what you wear.

Walking uphill is hungry work. On the flat you can tick along quite happily on the fuel you ate at breakfast, but add a thousand feet of ascent and your muscles are burning through glycogen far faster than your body can replace it. When those stores dip, you get the classic symptoms: heavy legs, a short temper, clumsy feet on a rough descent and a sudden conviction that the car park is further away than it was this morning. All of that is avoidable, and the fix is mostly about choosing the right kind of snack rather than simply carrying more of it.

Slow-release carbohydrates: the backbone of the rucksack

The bulk of your walking fuel should come from carbohydrates that break down gradually. Think oats, wholemeal and rye rather than white bread and sugary cereal bars. The fibre, fat and protein that come packaged with less-refined carbohydrates slow digestion down, so instead of a quick spike and an equally quick crash you get a steady trickle of energy for an hour or more.

Reliable choices that travel well in a rucksack:

• Oatcakes, plain or with a smear of peanut butter
• A dense flapjack made with oats, butter and dried fruit
• Malt loaf, sliced at home and wrapped in pairs
• Wholemeal or rye sandwiches with cheese, hummus or cold meat
• Cold boiled new potatoes with a little salt — odd sounding, but excellent
• Wholemeal pasta or couscous salad for a longer day out

Avoid packing only fragile, sugary things. They feel wonderful for twenty minutes and then leave you worse off than before, particularly on a chilly day when your body is working hard to stay warm.

Nuts, dried fruit and a little chocolate

Once the slow-release base is sorted, a mixed bag of nuts, seeds and dried fruit does the rest of the job. The combination works because each element behaves differently. Nuts and seeds bring fat and protein, which are calorie-dense and slow to digest, so a small handful genuinely sustains you. Dried fruit brings quicker sugars alongside a bit of fibre, giving a lift without the full crash of a fizzy drink or a sweet.

Then there's chocolate — and yes, a little is worth its weight in gold. It's morale as much as fuel. A couple of squares on the last climb of the day does something for your head that no oatcake ever will. Dark chocolate holds up better in a warm rucksack pocket, while milk chocolate is more welcome in February. Either way, keep it to a portion rather than a family bar, or you'll eat it all in the first hour.

A simple home mix — roughly two parts nuts, two parts dried fruit, one part chocolate — covers almost every eventuality and costs far less than individually wrapped bars.

Timing: little and often beats one big lunch

Most energy dips on the hills aren't caused by the wrong food, but by the wrong rhythm. Waiting for a proper lunch stop means you're already running on empty by the time you sit down, and a large meal then sends blood to your stomach just when your legs want it. Eating little and often is far kinder.

A practical approach is a small handful every forty-five minutes to an hour, starting before you feel hungry. On a long or hilly day, aim for somewhere in the region of 30 to 60 grammes of carbohydrate an hour, adjusted for your size, pace and how hard you're working. Sip water alongside — food without fluid sits heavily, particularly in cold weather when thirst is easy to ignore.

Packing and practicalities

Snacks you can't reach are snacks you won't eat. Keep the day's food in a hip belt pocket or the top of your rucksack rather than buried under a spare fleece, and decant things into small zip bags so you're not wrestling with a whole bag of nuts on a windy summit.

Weather changes the rules a bit. In winter, chocolate goes rock hard and cereal bars become unpleasant to chew, so keep a portion in an inside pocket where your body heat can soften it. In summer, chocolate melts into a mess — swap it for something more robust. Remember, too, that everything you carry up comes back down with you. Orange peel and banana skins are litter on the fells, not compost, and feeding sheep, ponies or wildlife does real harm. A small bottle of hand gel is worth the few grammes if you're crossing farmland.

Matching snacks to the walk in front of you

For a gentle two-hour stroll along a valley path, a banana and a flapjack is plenty. For a half-day with a couple of climbs, add oatcakes, a sandwich and your nut mix. For a full day in the hills or a long stretch of coast path, plan on roughly 1,500 to 2,000 calories: two rounds of sandwiches, malt loaf, a generous mix, some fruit and a little chocolate as a treat for the top.

Pack a bit more than you think you need, especially in winter or if the forecast is uncertain. The best snack is the one you're genuinely pleased to find at the bottom of the rucksack, halfway up a hill, with the cloud lifting and miles still to go.