Timing of exercise and food consumption have also been suggested as remedies, though their applicability in humans and practicality for most travellers are not certain, and no firm guidelines exist. There is very little data supporting the use of diet to adjust to jet lag. While there is data supporting the use of exercise, the intensity of exercise that may be required is significant, and possibly difficult to maintain for non-athletes. These strategies may be used both before departure and after landing. Individuals may differ in their susceptibility to jet lag and in how quickly they can adjust to new sleep–wake schedules.