Lunch and Snacks
Surprisingly, what you eat during the day (rather than breakfast and dinner) can be the major contributor to the total calories consumed in a 24-hour period. In fact, this is a good strategy to have, as 'little and often' is a better approach than eating large meals at infrequent intervals (I find a large lunch can really slow me down in the afternoon!).
Deciding what to eat is a mixture of what you want to eat and what's good for you. There's little point packing stuff that has the right list of ingredients if when you fish it out of your rucksack your heart sinks! Each person is different, but I find that I need a mix of savoury and sweet items to keep my interest going.
Of course, on a day walk you can take lovely fresh food from home, so I'll concentrate here on the kind of stuff that's appropriate for multi-day trips, when the number of calories per 100g weight is a number you need to become very familiar with.
Don't fall into the trap I did on one long trip: I stocked up from a shop using unfamiliar brands and over the next few days found that I really hated those unfamiliar brands and couldn't eat the food I'd sweated to carry on my back over those high passes! Taste and experiment before you go.
Cereal/snack bars (see here for the ones we sell) are popular, and I find that those closest to traditional flapjack are the nicest. They're good nutritionally as well, since oats release energy slowly over a long period: exactly what you need. Personally, I think energy bars and the like are overrated: I've eaten some which taste really awful, and if you work out the calories per 100g you may find that in some cases they are not actually that full of energy! Also, remember that different products are designed for different needs: in the outdoors you will typically need slow-release energy, not a rapid sugar rush.
Nuts are great: high in calories, good for protein and really good to eat. If you are exercising hard the fat content shouldn't worry you as much, as you are more likely to burn it off. Macadamia nuts are pretty high in terms of calories per 100g, but personally I prefer cashew nuts as to me they have more flavour.
Dried fruit of various kinds is delicious to eat: refreshing as well as tasty I find. My personal favourites include apricots, apples, bananas and sultanas. There's such a wide range available that you can experiment to find just the right combination for you.
Trail mix is a great way of combining nuts and dried fruit for a nutritious and tasty snack: you can keep dipping in through the day when you need a boost. We created our own mix which is available in 131g packs: a perfect size for one day.
Meat products are good to eat (if you're not a vegetarian...) and contribute well to your protein needs. Whether they are high in calories for the weight depends on the product. Pepperami is widely available: a pork salami with a long shelf life (although usually sold in supermarket chiller cabinets it does not need to be kept in a fridge), bags of flavour and lots of calories per 100g. Many cured meats (including salamis) will also keep just as well and may taste even better. Less widely available are jerky and biltong: basically dried meats (often beef) with flavourings: good for taste and protein, but lower in calories.
Chocolate and other confectionary is something you need to be a bit careful of. Foods high in sugar tend to give you an immediate high (a sugar rush), but this can be followed by a very unpleasant sugar crash when your blood suger level drops again. Personally, I find a little bit of chocolate (fruit and nut is my favourite) during the day can give me a nice lift, but I often leave my choccy ration until the evening to eat with my after-dinner coffee! A little hint for Brits travelling to the USA: be sure you like Hershey chocolate before buying too much: it has a rather particular and non-European taste which I'm not too keen on. Try Swiss chocolate, which is closer to what you're probably used to.