Food and dietary considerations
Clearly the primary issue in hot, dry conditions is providing sufficient water to prevent dehydration. Work undertaken at the Australian Institute of Sport in Canberra has shown that even very low levels of dehydration lead to significant losses in physical efficiency. Typical figures suggest that 2% dehydration can lead to reductions in physical efficiency by up to 20% among elite athletes. For a typical 70 kg walker, this translates to a loss of about 1.4 litres of fluid. Our experience shows that walkers can easily lose 6 kg (6 litres of fluid) in a single day, so preventing dehydration is both paramount and difficult.
It has often been said that moisture-laden food is best in hot, dry conditions as it is more palatable and easier to eat. While probably true for many walkers, this preference may derive from the substantial levels of dehydration affecting most walkers in hot, dry conditions.
Dehydration is best addressed with water, not moisture-laden food. If prevention of dehydration is properly tackled, the need for relatively moist foods for palatability becomes much less of an issue. Moisture-laden foods are heavy. Dehydrated food is lighter, so additional water can be carried.
Chapter 27 discusses food and outdoor diets in more detail, including a section specifically on food for hot, dry conditions.